About the only thing you can do is open the computer up, re seat the video card, blow the plug and socket out real well where the monitor plugs into the video card. If it still does it, it's probably the monitor.
Try plugging it in to another system if you have the luxary, make sure you set resolution and refresh rate the same as the old system for equal load on the poor monitor.
Welcome to the forum and good luck with the monitor problem- keep us informed please of your progress on this matter.
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