On Android 12, there was a change in how the Power button functions. Starting with this version, the default action for the Power button became launching Google Assistant.
However, it is possible to change this behavior so that the button once again turns off or restarts the device. To do this, follow the steps below according to your device model:
Samsung:
- Open the Settings menu.
- Select Advanced Features > Side Key.
- At the bottom, under Press and hold, tap Power off menu.

Other Manufacturers:
1. Open the Settings menu (swipe down twice from the top of the screen and tap the gear icon).
2. Select System > Gestures.
3. Scroll to the bottom of the menu and tap Press and hold the power button.
4. Turn off the Hold for Assistant option.