You're mid-message, mid-call, or halfway through a video, and suddenly your screen goes black and the phone restarts itself. Once might be a fluke. But when it keeps happening, it's a sign something genuine is wrong, and it's worth understanding whether the cause is something you can fix yourself or something that needs a technician's attention.
The honest answer is that random restarts can come from almost anywhere in the phone, from a single misbehaving app all the way through to a failing battery or water damage. Below, we break down the real causes in order of likelihood, what you can try yourself, and when it's time to bring your phone in.
If the restarts started right after a system update or after installing a new app, that's your first clue. Updates occasionally introduce instability on certain devices, particularly older models, and a poorly optimised or incompatible app can crash the system repeatedly, forcing a reboot.
What to try: Check whether the issue started after a specific install. If so, uninstall that app and see if the restarts stop. If it began after an update, check for a follow-up patch, since manufacturers often push a fix once an issue is widely reported.When your phone's storage is nearly full, the operating system struggles to run background processes smoothly. This can show up as lagging and freezing before eventually tipping into full restarts.
What to try: Clear out old photos, videos, and unused apps. On both iPhone and Android, checking your storage breakdown in Settings will usually show you exactly what's taking up the most space.A boot loop is a specific problem, where the phone never fully completes startup. Instead of reaching the home screen, it cycles back to the logo repeatedly. This makes the phone effectively unusable and often points to a deeper software corruption or a hardware fault that software alone can't fix.
Though less common than the causes above, malware can absolutely cause random crashes and restarts, particularly on devices that have been jailbroken or rooted, or that have installed apps from outside the official app stores. Weak passwords and unsafe downloads increase this risk.
What to try: Stick to official app stores, avoid sideloading apps from unknown sources, and if you suspect an infection, a factory reset (after backing up your data) is typically the most reliable fix.This is one of the most common hardware causes of random restarts, and it's often misread as a software problem. A degraded battery develops higher internal resistance and struggles to maintain stable voltage under load. When the phone suddenly needs a burst of power, the voltage can dip too sharply, and the system shuts down and restarts to protect itself.
When a phone gets too hot, whether from heavy gaming, extended video streaming, or being used while charging, it will sometimes restart automatically as a built-in safety measure to protect its internal components from heat damage.
What to try: Give your phone a break from demanding tasks, remove any thick case that's trapping heat, and avoid using it while it's actively charging if it feels warm to the touch.It sounds unlikely, but a power button that's physically stuck, whether from dust, pressure, or damage, can trick the phone into thinking the button is being held down continuously, which can trigger repeated restarts.
Any liquid exposure, even a small splash that seemed to dry out fine, can leave corrosion on internal components that causes intermittent faults, including random restarts that may not show up immediately. Similarly, a drop that's jolted an internal connector loose can produce exactly this symptom.
Software causes, a buggy app, low storage, or a pending update, are genuinely worth troubleshooting yourself first. They're free to try, low-risk, and solve the majority of restart issues.
While a failing battery, water damage, or a loose internal connector aren't things you can diagnose with certainty from the outside, opening a modern phone to investigate risks turning a fixable problem into a more expensive one. If you've worked through the software checklist above and the restarts are still happening, particularly if you're seeing signs pointing to the battery or you know the phone has had any liquid exposure, it's time to have it properly assessed. Book your repair today and let our expert team take it from there. Repairs start from just $59, and every job is backed by our price match guarantee.
A phone that keeps restarting is annoying, but it's almost always fixable once you know the actual cause. Start with the free, low-risk software checks, a buggy app, low storage, or a pending update. If those don't solve it, particularly if you're noticing signs pointing to the battery, overheating, or any past water exposure, let a professional take a proper look rather than guessing your way through a hardware issue. Get in touch with our team or book your device in for a diagnostic, and we'll get to the bottom of it properly.
This is a classic sign of a degraded battery. As batteries age, they struggle to maintain stable voltage under load, and the phone shuts down and restarts to protect itself, even if the displayed percentage still shows plenty of charge remaining.
A factory reset resolves the vast majority of software-caused restarts, including most buggy apps, corrupted files, and minor system glitches. However, it won't fix a hardware fault like a failing battery, damaged power button, or water damage, if the phone still restarts after a clean reset, the cause is almost certainly hardware.
It's not usually dangerous on its own, but a swollen battery, one of the possible causes, can be a genuine safety concern. If you notice any swelling or bulging around the back panel or screen, stop using the phone and have it looked at professionally as soon as possible.
Pricing depends on your exact phone model, but repairs at Phone Parts NZ start from just $59, with individual battery parts priced on our website and professional installation available.
Occasional overheating that triggers a protective restart typically won't cause lasting damage. However, repeated or prolonged overheating can accelerate battery degradation over time, so it's worth addressing the underlying cause, such as heavy background app use or charging while gaming, rather than ignoring it.
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Get everything you need for your phone repairs in one convenient place. Plus, take advantage of expert installation services and exclusive perks for new customers—including free shipping!
