iphone wont turn on

Try force restarting:

press vol up then vol down then press and hold the side/power button till the phone shuts off. Continue holding till you see the Apple logo and then let go.

if not, try recovery mode:

press vol up then vol down then press and hold the side/power button till the phone shuts off. Continue holding even if you see the Apple logo, and let go when you see the connect to iTunes of connect to computer logo.

then plug your iPhone in to your computer and select update iPhone. If it doesn’t work select Restore iPhone. Restoring will erase all data in the iPhone.