Why does my phone keep restarting by itself?
Four causes, distinguishable by pattern: a failing battery that cannot sustain peak current, an app or system fault, overheating, or physical damage. The pattern tells you which.
- Difficulty
- intermediate
- Time
- 40 min
- Read
- 5 min
- Safety
- caution
Short answer
Note when it happens. Restarts under load — camera, games, calls, navigation — with a battery health figure that has fallen are a battery that can no longer supply peak current, and a replacement fixes it. Restarts at random with a healthy battery point at software: use safe mode on Android, or remove recent apps on iOS. Restarts when hot are thermal. Restarts after a drop or a soaking are hardware.
Random restarts feel catastrophic and usually are not. The useful move is to stop treating it as one problem and start recording when it happens, because the four causes have almost non-overlapping patterns and the pattern is diagnostic in a way that any amount of resetting is not.
Safety
Step by step
- Keep a note for two days.Time, battery percentage, what you were doing, whether the phone was warm, and whether it was charging. Six entries usually make the cause obvious, and without them you are guessing. This is the single most valuable thing you can do here.
- Check the battery health figure.Both platforms report battery health or capacity in the battery section of settings, with Android varying by manufacturer. A figure well below its original capacity, combined with restarts under load or at a battery level that is not actually zero, is a failing cell — it cannot hold voltage under a current spike and the phone protects itself by resetting.
- Notice whether it happens at a consistent percentage.A phone that reliably dies around 20 or 30 per cent, then shows a higher figure when plugged back in, has a battery whose remaining capacity the phone can no longer estimate. That is a battery replacement, and on a phone otherwise in good order it is usually well worth doing.
- Check the temperature relationship.Restarts while navigating in a car on a sunny day, gaming, or on a wireless charger are thermal protection working. Take the case off, keep the phone out of direct sun, and stop charging while running something heavy. A phone that shuts down rather than restarts, with a temperature warning, is the same mechanism.
- Test the software on Android with safe mode.Boot into safe mode and use the phone for a day. If the restarts stop, an installed app is responsible and you can find it by removing recent installs in halves. If they continue, the cause is the system or the hardware.
- On iOS, remove recent apps and check for a pending update.There is no safe mode. Remove anything installed in the fortnight before the restarts began, install any pending system update, and check whether the phone is nearly full — a phone with almost no free space misbehaves in exactly this way.
- Free space and check for a stuck update.A phone running at almost no free storage restarts, and a system update that partially applied and failed can leave the phone in a restart loop. Free at least a tenth of the capacity and let any pending update complete on wi-fi while plugged in.
- Consider physical causes if it followed an event.Restarts that started after a drop, a soaking or a battery replacement point at a loose connector, corrosion, or a poorly fitted part. A repair shop can inspect this; nothing you do in software will fix it.
- Use a factory reset as the deciding test.If you have exhausted the above, back up, factory reset, and use the phone for a day set up as new without restoring. Restarts on a clean phone mean hardware. No restarts means it was software or an app, and you can restore selectively.
If it doesn't work
Restarts only while charging
Cause: A failing cable or adapter, a dirty or damaged charging port, or a battery that cannot handle the charge current — Fix: Try a different known-good cable and adapter first — it is the cheapest possible test. Then inspect the port for lint under a bright light. If both are fine, suspect the battery.
Restarts in a loop and never reaches the home screen
Cause: A failed update, corrupted system storage, or hardware — Fix: This is beyond ordinary troubleshooting. Recovery mode — a button combination during boot, published per model — can reinstall the system without erasing, and failing that, erase and restore. If neither works, it is hardware.
Restarts stopped after uninstalling one app but it was an app you need
Cause: That app conflicts with your OS version or another app — Fix: Reinstall it fresh rather than from a backup, check for an app update, and contact the developer — a reproducible restart is a bug they want to hear about. In the meantime use the service's website.
Restarts and the date and time are wrong afterwards
Cause: A failing battery losing power entirely, or a hardware fault — Fix: This pattern — losing the clock — is a strong hardware indicator. Have it looked at rather than continuing to troubleshoot software.
Questions people ask
Is it worth replacing the battery on an old phone?
If the phone is otherwise fine and still getting security updates, almost always yes — a battery replacement typically costs a fraction of a new handset and restores the phone completely. If it is out of software support, put the money towards a replacement instead.
Could it be a virus?
Very unlikely on iOS and unlikely on Android if you install only from the official store. Malware generally wants to stay hidden, and a phone that restarts constantly is useless to it. Look at battery and software first.
Does a restart lose my data?
No. An unexpected restart may lose whatever you had not saved in the app you were using, but nothing stored is affected. Repeated restarts during a system update are the one exception and can leave the phone in a bad state.
The phone restarts when I take a photo. Why the camera specifically?
The camera, especially with flash or video, is one of the highest instantaneous power draws on a phone. It is the classic trigger for a battery that can no longer supply peak current — a textbook symptom of a cell that needs replacing.