You can release the buttons when you see the menu.

If you’d rather reboot your phone, just tap the green Restart icon instead.

Once your phone is powered down, you can easily turn it back on by pressing and holding the side button.

If you’d rather reboot your phone, just tap the green ‘Restart icon instead.

Once your S21 is off, you can easily turn it back on by pressing and holding the side button.

Press and hold the side button (below the volume keys) on the right side of the phone. If you haven’t already, sign in to your Samsung account when prompted. Select your language and tap Start. Review the terms and tap OK to agree. [2] X Research source

To turn your phone back on after powering down, just press and hold the side button.

Remapping the side button will disable Bixby, so you should only do this if you don’t plan on using Samsung’s voice assistant. [3] X Research source

Now you can power down and restart your S21 or S22 by pressing and holding the side button for a few seconds and tapping Power Off or Restart.