Did you try this with the cover off? I find this test tells me quickly if it's just the old issue of overheating in a case.
Hello everyone,
I've bought myself an Nvidia gtx 1050 TI a few days ago, because my gtx 960 kept heating up every few minutes (regardless of the current program) which caused a massive FPS drop and made every animation on the screen stutter. When I used my PC after installing the new card, it worked fine, but after a few hours, the same problem started occurring again, and it hasn't stopped. As said, temperature goes up=massive lag, temperature goes down=everything normal. I guess this has something to do with either my power supply (HEC-450TC-4WEM, 450W), or my motherboard, which I'm not an expert with. Also if it helps, my pc is the Medion Erazer i73000 C171, even though I don't think anyone will recognize it. I apologize I didn't make it too complicated, and I thank everyone for trying to help in advance.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic