I always say “flock of cows” to bait someone into saying “herd of cows” so that I can say “of course I’ve heard of cows!” Watching their faces is priceless.

Does it happen faster the 2nd time around? Probably a heat issue. Make sure the fans are working and the heatsink fins are clear of dust and debris. Try that first, and run a gpu stress test https://mprep.info/gpu/ but it could also be drivers as others have mentioned, or even a faulty or incorrectly seated ram module.