LG monitor help

So I just bought a 20 inch LG Flatron W2052TQ monitor about a week ago for my ps4 on Kijiji. It works fine for about 20 minutes which then It'll start to shut on and off again randomly. I know it's not the ps4 because the game still runs in the background. The only way I know how to fix this is to lower the resolution to 480p which is not good, but anything higher than that will cause the problem to start occurring. Is there anyway that I could stop this from happening?
Thanks!
 
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