Press and hold the Power button on the side of the phone.
Wait for the power menu to appear on the screen.
Tap on the "Restart" option.
Confirm if prompted to proceed with restarting.
The phone will shut down and power back on automatically.
Alternatively, for some newer models:
Press and hold Power + Volume Up for 3 seconds to bring up the power menu.
Swipe or tap on Restart as shown.
The device will reboot within a few seconds.