1. Connect iPhone to PC
It is possible that you can be stuck in a situation where your iPhone has a faulty power button and it shuts down unexpectedly. In such cases, you can try to connect your iPhone to a PC and wait for a few seconds or minutes for it to boot. In most cases, if your iPhone has enough charge, it should boot automatically into iOS. If not, try the step mentioned below.
2. Force Restart iPhone
If your iPhone is not booting even after pressing the power button, you can try force restarting it to see if that helps. Depending on which iPhone you have, the steps to force restart your iPhone will be different. On iphone 8 and newer iPhones without a home button, you need to press the Volume up button followed by the Volume down button and then quickly press and hold the Side button for at least 7-10 seconds. Your iPhone should boot and you should see an Apple logo on its display.
3. Charge It!
Ok, this is a simple one. If your iPhone has suddenly stopped booting and the above measures were in vain, you should put your device on charge. Do not try to immediately boot it after putting it on charge. Instead, let it charge for at least 10-15 minutes and then try to power it on. If you have a relatively old iPhone with a weak battery, it is possible that the battery is no longer capable of holding a charge after a certain threshold. In case your iPhone boots after being on charge for around 20-30 minutes, it is recommended you get its battery replaced since it can no longer hold a charge properly.
4. Take It to Service Center
If none of the above steps worked in reviving your iPhone, the only option you now have left is to take it to your nearest Apple service center. If your device is in warranty, you can take it to an Apple store or an authorized Apple service center to get it repaired. Since the device will be in warranty, Apple will repair or replace it for free.
