My uneducated amateur guess would be overheating, or incompatibility between said games and graphics card driver (drivers can be updated). Some games will make some graphics card work harder than they should, and these games don't necessarily have better graphics. But when we talk about overheating you can have the graphics card overheating or the cpu overheating or even both.

My graphics card used to overheat after a while playing some games and that would make the computer start freezing like hell and even crash even though this graphics card has a huge fan. I didn't need to solve that issue though because I coincidently stopped playing for a while.

To confirm (or rule out) overheating you can try to run the desktop in the coolest place you can find to see if it noticeably holds up more than usual without freezing (don't put your computer in any kind of food refrigerator). If it does, then it's overheating. If it's overheating then you have to find out if the graphics card is overheating or if the cpu is overheating.

If you confirm that the problem is related to either the graphics card or the cpu overheating then I would try to check for dust in the refrigeration system (fans and heatsinks), if there's dust clean it up; also beef up the refrigeration on your machine getting new case fans if there aren't enough. You have to build an air flow, preferably with a vent on the bottom for cool air to rise up, and another vent on the top of the case for the hot air to leave more efficiently), and put the case in a cooler place, etc

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