Phone keeps restarting on its own? How to find the cause of random reboots

The single most useful test is Safe Mode (Android), which loads the phone without third-party apps. If the reboots stop in Safe Mode, a downloaded app is the cause; if they continue, the problem is deeper. On iPhone there's no Safe Mode, so note whether reboots cluster around one app or happen at random.

Also note the pattern: reboots tied to a specific app or action point at software; reboots that happen at random, on charge, or when the phone is hot point at hardware.

Most random-reboot cases are software and cost nothing to fix:

• Update the OS and all apps — reboot bugs are frequently patched
• Uninstall recently added apps, especially anything that crashed around the time it started
• Free up storage if the phone is nearly full (low space causes instability)
• Reset settings (keeps your data) as a step up from a restart
• Back up and factory reset as a last software resort before suspecting hardware

A worn or failing battery is a leading hardware cause. When a tired battery can't deliver a sudden burst of power, the phone shuts down or reboots — often around 20–40% charge, in the cold, or under load. Check battery health (iPhone: Settings › Battery › Battery Health; below ~80% is worn), and look for any swelling, which means stop using it and replace it now.

If software and battery check out, the cause is likely on the board:

• Reboots that started after a drop or water exposure
• Reboots that get worse as the phone heats up (a possible short)
• A continuous boot loop that never reaches the home screen
• Reboots paired with other faults like signal loss or charging problems

Battery-versus-board is worth confirming rather than guessing, since one is a quick swap and the other is chip-level work. iTweak runs an 80-point diagnostic, shows you the actual fault before quoting, and repairs Apple and Android with warranty and a digital invoice. If we misdiagnose it, you don't pay.