have you tired switching your computers coffee to decafe??? and letting it get it eight hours of sleep at night
little sleep joke there...i would try the monitor on another pc or laptop and see if it powers off and does not turn back on.
sounds more like a bad power supply or control board in the monitor.
you can see if there any bios updates for your pc. if it not a bios issues with the mb the only thing left would be a issue with your power supply.