Monitor blacking out

My monitor blacks out at 25 second intervals for about 3 - 4 seconds each time. The screen goes completely black and then comes back like normal. Don't know if it's a monitor problem, a video card problem, or some sort of a software glitch. Anyone seen anything like this before?

 

Is this a recent problem? Do you have another monitor to swap to check if it's the monitor? And do you have another computer to put this monitor on to see if it does the same thing?