Press and quickly release the Volume Up button
Press and quickly release the Volume Down button
Press and hold the Side button
Keep holding until the Apple logo appears
Release the Side button
If the iPhone has a Home button, press and hold the Home button and the Side button together
Keep holding until the Apple logo appears
Release both buttons
If the screen still stays frozen, connect the iPhone to a computer
Open Finder on Mac or iTunes on Windows or older macOS
Put the iPhone into recovery mode
Choose Update first if available
If needed, choose Restore
If the iPhone still does not respond, let the battery drain completely
Charge it again and restart the device