When holding down the Power off button on the screen, nothing happens till I let go, and then the system just powers off.
This guide is not exactly for your model, but it will probably work on your model, too:
Turn on safe mode
- Turn device off.
- Press power button.
- When the "Acer" logo is displayed, release the power button.
- Immediately after releasing the power buton, hold the volume down button.
- Keep holding down the volume down button until the phone finishes rebooting.
- Release the volume down button when you see
Safe Modeappear in the lower left corner of the screen.