How to Fix an Apple iPhone 13 that keeps rebooting unexpectedly in iOS 15.2.1

This highlights a few potential solutions to a performance-related issue on a new iPhone that suddenly shuts down and reboot on its own. Read on to learn how to fix an Apple iPhone 13 that keeps rebooting unexpectedly in iOS 15.2.1.

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When it comes to performance stability, Apple devices are highly reputed than many of their counterparts. But it turned out that not all iPhone owners agree with this notion. 

In fact, a number of iPhone 13 owners were raising complaints regarding an unusually atrocious behavior about their new iPhone that’s randomly rebooting on its own.

Such behavior is like the BSOD symptom in Windows computers that usually happens when the device is experiencing a so-called kernel panic due to a fatal software error or faulty hardware.

If you encounter the same issue on your new iPhone and need some input on how to fix it, then you can try any of the outlined solutions below to eliminate software-related culprits.

What triggers an iPhone to crash and reboot on its own?

Random restarts, lags and freezes are just a few of the many symptoms of performance deterioration among computers and mobile devices.  

These symptoms are typically transpiring on a device after several months of continuous usage. But there are also a number of new devices that succumb to the same problem. And the new iPhones are no exception. 

Such a problem usually happens because something from within the system is triggering it. There are many factors that can trigger such atypical behavior to occur on a new device. Among the known culprits include software bugs, malware, and rogue apps. In worst case scenarios, random restarts or boot loops are indications of hardware damage.

Before rushing to a service center, ruling out software-related culprits is highly recommended.

To give you some input on what to do whenever you bump into a similar issue on your iPhone 13 in iOS 15.2.1, I’ve mapped out a few potential solutions that might be able to help you.

Fixing an iPhone 13 that keeps rebooting unexpectedly in iOS 15.2.1

Before you begin troubleshooting, make sure that your iPhone is sufficiently charged and is not experiencing rapid battery draining issues. Note that an iPhone may also shut down unexpectedly due to a bad battery.
If everything is good with the iPhone battery, then you may go ahead and start ruling out individual culprits from within the software layer of the device. Just try any of these outlined procedures and see if the problem will be resolved.

Solution #1: Install pending updates.

Software updates are not only pushed to bring in new features but more importantly, they contain essential fix patches to get rid of existing bugs that caused havoc to certain devices. This applies to both app updates and firmware updates released by software developers and the device manufacturers.

If you haven’t enabled the auto-update feature on your iPhone, then you will need to manually download and install pending updates for both apps and iOS.

Before updating, your iPhone must have ample storage, sufficient battery life and stable internet connection.
Once everything is set, you can go ahead and check for new updates available.

To check for a new iOS update on your iPhone 13, just follow these steps:

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  • Go to Settings.
  • Tap General.
  • Tap Software Update.
  • If a new iOS version is available, read the software information then tap Download and Install.

Follow the rest of the onscreen prompts to finish updating your iPhone.

To check for pending app updates on the iPhone 13, refer to these steps:

fix iphone13 keeps restarting unexpectedly ios1521 update apps
  • Open the App Store.
  • Tap on your profile icon then scroll to view pending updates and release notes.
  • To update individual apps, tap the Update button next to the name of the app.
  • Otherwise, tap Update All to download and install multiple app updates at once.

After updating, reboot/soft reset your iPhone. This is imperative to ensure that all recent software changes are properly implemented. It’s also a way to clear out cache including any corrupted residual data that might have caused certain apps or the device itself to act up. Rebooting also refreshes apps and system services on the device.

Solution #2: Offload Unused Apps.

As mentioned earlier, random restarts can also be attributed to a memory issue like when the iPhone storage is running low. 

To address memory-related issues on an iPhone, enabling the built-in feature called Offload Unused Apps can help.

With this feature enabled, all apps that are inactive or unused for a long period of time will automatically be deleted whenever the phone realizes that it’s running low on storage space.

Offloaded apps will then be deleted but all data and documents for those apps will be retained. The apps’ data will therefore become accessible as soon as you redownload the offloaded app from the App Store.

To enable this feature on the updated iPhone 13, just follow these steps:

fix iphone13 keeps restarting unexpectedly ios1521 offloadunusedapps
  • Go to Settings.
  • Tap App Store.
  • Tap to turn the Offload Unused Apps switch ON.

Meanwhile, if the sudden reboot issue occurs only when using a certain application, then it could be an isolated problem with that app. Should this be the case, manually offloading the problematic app is recommended.

Just follow these steps to manually offload individual app on an iPhone 13:

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  • Go to Settings.
  • Tap General.
  • Tap iPhone Storage.
  • Find and select the problematic app from the list.
  • Tap Offload App on the App info screen.
  • Read the warning prompt then tap Offload App to confirm.

The app will then be removed from the iPhone but all data and documents for that app remain.

Solution #3: Optimize storage.

Aside from offloading apps, random reboots that are tied to low memory on the iPhone can also be resolved by optimizing storage.

To do this, you can delete old and unwanted contents, unused apps and messages. Doing so will free up some storage space and thereby makes your iPhone perform better and stable again.

This is highly recommended if the remaining (available) storage space on your iPhone is already less than 2 gigabytes.

To check your iPhone’s current memory status and see how much is the used and available storage, just access the iOS 15 storage menu with these steps:

fix iphone13 keeps restarting unexpectedly ios1521 optimizestorage
  • Go to Settings.
  • Tap General.
  • Tap iPhone Storage.

There  you can view more details about the used and available memory and see which from your apps is utilizing more memory.

Aside from deleting old and unused content, moving other files from the iPhone to other storage locations like iCloud or iTunes drive is also another option.

Solution #4: Reset all settings.

Utilizing the built-in reset commands on your iPhone can also be deemed among other potential solutions especially if the random restarts instigated from a recent download, an update or after a series of alterations on the system settings.

Performing this reset does not affect any saved data on your iPhone internal memory and so you won’t lose any important files in the process.

Just follow these steps whenever you decided to go for this reset:

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  • Go to your Home screen and then open the Settings app.
  • Scroll to and tap General.
  • Tap Transfer or Reset iPhone to proceed.
  • Then tap on Reset. 
  • On the succeeding menu, tap Reset all settings from the given options.
  • Enter your device passcode if prompted.
  • Tap the option to confirm all system settings reset on your iPhone.

After the reset, all default settings are restored. This means the need for you to reconfigure individual settings and re-enable necessary features so you can use them again on your phone.

Solution #5: Restore factory defaults.

If the previous reset doesn’t solve the problem, then you may have to resort to a full system reset or factory reset. Doing so will wipe everything from your iPhone system including downloaded apps and files, custom settings, network configurations, and other added information. 

Should you wish to proceed, back up all your important data if possible. You can back them up to  your iCloud account or to a computer directory/folder using iTunes.

Performing a factory reset on an iPhone can be carried out through the Settings menu or using iTunes on a Windows computer or Finder on Mac. 

Since the device is not performing stable, performing a factory reset through iTunes would be a better option. This way ensures that the reset won’t be interrupted by an unexpected boot loop.

To restore your iPhone 13 to its factory defaults using iTunes, just follow these steps:

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  • Connect your iPhone to the computer using the Apple-supplied USB cable.
  • Open iTunes then wait for it to detect your iPhone.
  • When connected, select your iPhone in iTunes then click the Restore button.

Follow the onscreen instructions to restore your iPhone from a previous back up or do a fresh iOS install to set up your device as new.

Is your iPhone still rebooting unexpectedly?

The above solutions are tagged among the basic workarounds when dealing with software-related performance issues in iOS devices. If none of the suggested procedures work, then resorting to more advanced solutions can be deemed among the last resort.

Should you wish to continue troubleshooting, your next options would be as follows:

1. Recovery Mode Restore. 

This will put your iPhone in recovery state and then allows iTunes to wipe the device and restore the defaults. 

Recovery mode is a failsafe in iBoot that is primarily used to revive a corrupted iPhone with a new version of iOS or a stable iOS backup. 

Restoring an iPhone in recovery mode can help repair fatal system damages. But the main downside is that all your files will be deleted.

2. DFU Mode Restore.

DFU stands for Device Firmware Update, a special iOS state where iTunes can communicate and access the device interface even without activating the bootloader.

Once your iPhone enters a DFU state, iTunes would be able to restore it and erase any critical errors that might have made the iPhone system vulnerable.

But similar to a recovery mode restore, performing a DFU mode restore also deletes everything from the iPhone storage.

In return, you will have a chance to do a fresh iOS install or restore your iPhone from a flawless iOS backup.

3. Third-party iPhone Repair Tools.

Aside from iTunes, there are plenty of other tools that you can use to repair critical system issues on an iPhone. These tools can be downloaded for free or via one-time purchase. 

Resorting to third-party iOS repair tools can be considered as the last resort whenever iTunes fails to fix your iPhone.

Among the widely used tools for this purpose include AnyFix, PhoneRescue for iOS, Dr. Fone, FonePaw iOS system recovery, Tenorshare ReiBoot, FoneLab iOS System Recovery and JoyoshareUltFix, to name some.

Just pick the tool that meets your demands and is compatible with your computer.

Seek More Help

If none of the above solutions worked and your iPhone continues to restart on its own, then there’s a higher chance that hardware damage is present. At this point, taking your iPhone to the nearest Apple Genius bar is recommended. This way you can ask an authorized technician to diagnose your iPhone’s hardware components in order to figure out what triggers the occurrence of random restarts.

Should this be found to be a hardware issue, getting it repaired is definitely a definite solution. If your iPhone is still covered by warranty, then you better talk to your device carrier on how to avail of the warranty instead.

Please keep posted for more comprehensive iOS tutorials and troubleshooting guides on this site. Or you can check out this YouTube channel to view more comprehensive tutorial and troubleshooting videos including recent iOS devices.

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