What’s up with our desktop monitor?

I really dunno why our desktop monitor is acting up these days. Our guest here at home is the one using our desktop PC and it’s embarrassing when at times she is so engrossed working at our desktop PC when suddenly the monitor goes blank, and a message flashes before it turns off: “monitor going to sleep”.

This crazy behavior happens at no definite time of the day. It just happens. What do you think??? Could it be some virus? Or could it be that the power management automatically turns off the monitor? Ugh… I am running out of answers. If it were some computer memory issues, I could just have easily solved it with replacing the chip. But an LCD monitor that goes blank on you is just difficult to troubleshoot.