Computer suddenly went into safe mode

Hello,
My computer suddenly went into safe mode and the screen is completely blank on the monitor it is black. The orange light is on. It first turns on to green and then after a few seconds it goes back to orange. If I press the plus button it says in power save mode press computer power button or any key on keyboard or move mouse when I try that nothing happens the screen is still completely black. The light is still orange but the computer power light is on