while off and after say giving it 10 minutes to charge plugged in and leave it plugged in - try holding down the power button and the volume down button for about 10 secs together at same time. Release both at same time and wait 3-5 seconds the screen should show a hard reboot screen in weird DOS green fonts - select the continue with reboot up one and it will start up again - happens to me a lot and I am still using it! Best Phone EVER!