Video card temperature fluctuates strangely

In general, I sat playing GTA 5 and then bang a black screen and also the game seemed to turn off and then the video card in games began to warm up strangely, for example, it used to be in forza 5 - 52 stably now I go in somehow strangely 46 degrees I think what kind of nonsense then some kind of loaded the stage and bang is 70 degrees, but if it were loaded and that’s it, if it’s loaded at 70, it will be there 68 70 and the fan is sharply constantly back and forth, and in all games it’s not a miner! I even reinstalled Windows, I think the old driver can install a video card - 1660 super palit help kind people please!!!