Use the Quick Settings menu and tap Restart if available
Use the Accessibility menu and select Restart or Power options
Plug the phone into a charger and see if it wakes or reboots from the screen
Use a scheduled restart feature if your phone has one in Settings
Use a hardware key combination to force restart
For Android, try holding Volume Down and Power together if the power button still responds partially
For iPhone, use AssistiveTouch and tap Device, then More, then Restart if available
If the screen is frozen, perform a force restart using the correct button combination for your model
If your phone supports it, use voice assistant commands to restart the device
If none of these work, let the battery drain completely, then recharge and power it on
If the phone is unresponsive, seek service or repair for the power button