When your iPhone 15 starts restarting on its own, it's more than just an annoyance. It can interrupt calls, disrupt your work, and make you worry about the health of your brand-new phone. The good news is, this is often a software hiccup you can fix yourself.
Before you start, it's a smart move to make sure your data is backed up. You can do this quickly via iCloud by going to Settings > [Your Name] > iCloud > iCloud Backup and tapping "Back Up Now." This protects your photos, messages, and app data just in case.
I'd start with the simplest fix first, which is often all you need.
Perform a Force Restart
A force restart is the digital equivalent of taking a deep breath for your iPhone. It clears out minor software glitches in the memory without touching your data. For the iPhone 15, the process is straightforward.
Quickly press and release the Volume Up button. Then, quickly press and release the Volume Down button. Finally, press and hold the Side button (on the right) until you see the Apple logo appear on the screen, then let go.
This takes about 10 seconds and can stop a random restart cycle immediately.
Update iOS and Your Apps
Your iPhone 15 runs iOS, and since it's a new model, Apple is frequently releasing updates to squash bugs. An outdated system can definitely cause instability. Head to Settings > General > Software Update.
If an update is available, tap "Download and Install." Make sure your phone is plugged in and on Wi-Fi. While you're at it, check your apps too. Open the App Store, tap your profile icon in the top right, and scroll down to see pending updates.
Tap "Update All" to make sure no app is causing a conflict due to old code.
Check for a Problematic App
Sometimes, one misbehaving app is the troublemaker. Think about when the restarts began. Did you install a new game or utility right before the issue started? You can try removing recently downloaded apps to test.
Another method is to check your analytics logs. Go to Settings > Privacy & Security > Analytics & Improvements > Analytics Data.
Look for log entries that start with the name of an app you suspect. If you see the same app crashing over and over, that's a strong clue. You can offload it from Settings > General > iPhone Storage to remove the app but keep its documents.
Review Your Charging Setup
This is a key tip for the iPhone 15. Since it's the first iPhone with USB-C, using an old or incompatible cable can cause power delivery issues that might lead to unexpected behavior, including restarts.
Make sure you're using a USB-C to USB-C cable, not a Lightning cable. Also, try a different power adapter, preferably one that supports USB Power Delivery (PD). The iPhone 15 can charge at up to 27W with a compatible adapter.
If you use MagSafe, ensure there's no debris on the back of your phone or the charger. A thick or metal case can also interfere with charging and cause overheating, which triggers safety shutdowns.
Check the 80% Charge Limit
Introduced in iOS, the 80% limit feature is designed to prolong your battery's lifespan. If you have this turned on, your phone will stop charging at about 80%.
Some users mistake this for a problem, but it can also cause confusion if the phone behaves differently on a partial charge. Go to Settings > Battery > Battery Health & Charging.
Look for "Charging Optimization." If it's set to "80% Limit," try switching it to "Optimized Battery Charging" or "None" to see if it affects the restarting issue. This setting is purely about charging logic, but it's worth ruling out.
Free Up iPhone Storage
When your storage is critically full, the operating system doesn't have room to breathe. This can lead to all sorts of instability. Go to Settings > General > iPhone Storage.
The system will show you a breakdown and may offer recommendations like reviewing large attachments or offloading unused apps. Try to keep at least a few gigabytes free. If you're near capacity, deleting some old videos or offloading apps you don't use can make a big difference.
Reset All Settings
This is a more substantial step, but it won't delete your photos, messages, or apps. It will, however, reset every single setting on your phone back to factory defaults.
That means your Wi-Fi passwords, wallpaper, privacy permissions, and keyboard dictionary will be wiped. Go to Settings > General > Transfer or Reset iPhone > Reset.
Choose "Reset All Settings." You'll need to enter your passcode. After the phone restarts, you'll have to reconnect to Wi-Fi and re-customize some things, but it can resolve deep-seated configuration conflicts.
Restore via Recovery Mode
If your iPhone 15 is stuck in a constant restart loop, recovery mode is your tool. This lets you reinstall iOS completely. You'll need a computer with a USB-C port (or an adapter) and the Finder app (on Mac) or iTunes (on Windows).
Connect your iPhone to the computer with a cable. Quickly press and release the Volume Up button, then the Volume Down button. Immediately press and hold the Side button.
Keep holding it even after you see the Apple logo. Wait until you see the recovery mode screen (a cable pointing to a computer icon), then let go. Your computer will prompt you to either Update or Restore. Choose Restore to install a fresh copy of iOS. This will erase all data, so it's a last resort.
Consider a Hardware Check
If you've tried every software fix and the random restarts continue, it's time to consider the physical device. While less common, issues like a faulty battery connection or a logic board problem can cause this.
Since the iPhone 15 uses an eSIM primarily, there's no physical SIM card to remove and re-seat like on older models. Your best course of action is to contact Apple Support or visit an Apple Store.
They can run remote diagnostics to check for hardware flags and advise if a repair is needed. Given the phone's age, it should still be under the standard one-year warranty if you bought it new in 2023.
