Normally this doesn’t happen that your iPhone keeps shutting down and restarting all of a sudden. But when it does it is really a matter of concern for you. Either you think of replacing it or affording to buy a new phone. New phone models do get replaced but the old ones that are out of replacement period you can’t do anything about it. This problem of restarting on and off is found in bit older iPhones i.e. iPhone 4s, 5, 5c, 5s models that upgrade to iOS 8 or later. Also iPhone 6 and 6 plus reboot randomly after upgrading to iOS 9.
Fine below the ways, in which you can try to fix your iPhone that keeps shutting off, restarting or freezing.
Turn ON/OFF Cellular on your iPhone
You might think this as crazy but this issue can be seen sorted out by turning off your cellular data and then turning it on again. To do so go to settings > Cellular/Mobile > Turn On/Off Mobile Data.
Try to Reboot your iPhone
To reboot your iPhone, hold the power button and home button simultaneously for a few seconds. The Apple logo will appear on the screen and your iPhone is rebooted.
Try to Reset your iPhone
To reset your iPhone, go to Settings > General > Reset > Reset All Settings.
Look for a Faulty App
There might be a faulty app loaded on your iPhone. Though App Store is safe and protected to download apps but there are apps that aren’t really good for the health of your iPhone. One of these, possibly, could be ruining your iPhone experience. Maybe you have downloaded any new app that triggered the issue. It doesn’t matter if it’s a popular app or an app that no one has ever heard of. Just try deleting it.
Delete the app > Reboot your iPhone > Sync with iTunes and see if this sorts the issue.
Try to Restore from an Old Backup
Connect your iPhone to iTunes on the system and then restore from an old backup. In case you got lucky, things will be back to normal.
Try Recovery Mode and Restore
This could be the best possible solution you could ask for. Again, it’s tougher to implement if your iPhone keeps shutting off or rebooting every two-three minutes.
Hold down the power and home button till the screen goes blank.
Next, connect to iTunes. It will “detect” the iPhone in “recovery mode.”
You can only restore now so restore your iPhone.
If things went well, you’ll have an iPhone that’s ready to be setup. You’ll have to try setting it as new because you don’t want to get the old problem again.
Try Using ReiBoot
You can go for this option without losing your data on your iPhone; this option can bring your iPhone back to normalcy.
Connect your iPhone that is trapped in reboot loop problem to your computer via a USB cable. Run ReiBoot. In the Interface, click “Enter Recovery Mode” to put iPhone into recovery mode.
Once ReiBoot puts your iPhone into recovery mode, click “Exit Recovery Mode” and ReiBoot will force your iPhone to restart. Wait for a few seconds and you can see your iPhone reboot to normal.
Time to Replace iPhone Battery
Battery, sometimes, could play a culprit. When every above option fails to give any result, you can go for the replacement of your iPhone battery. One that needs you to take the device to the Apple Store, after all.
Hope these ways work for you to solve the issue.