no signal on monitor

no signal on monitor

Anyone can help me? I've been having the same PC problem, my setup boots up to the windows desktop, and randomly having a black screen, while the system unit is still on. It's &&^&^$^ absurd, since I've tried to record how long my pc last before having the problem, and it goes from 18 minutes, to 4, to even 55 seconds after the windows desktop appears. I'm recording the time as the windows desktop appears.