I have been having this problem for a really long time, tried various fixes but noone of them worked. Especially when playing games, it's becoming really unplayable, it's going normally when I restart pc for the first 30 minutes or when I remove and reinstall new driver. Just don't tell me try clean reinstall driver and that sorta things, no I have tried many different drivers, I dont even use the overclock I know you are going to say, remove any overclocking program, I dont have that.
Here is my Graphic Card : MSI HD 7750 OC | TechPowerUp GPU Database
GGPU-Z Sensors and I'm currently in game. yet my clocks are back to idle
I also added GPU-Z Sensor Log. As you can see at 1:58:30 I opened game and it was going smooth untill 2:02:58 and everything went back to idle, stuck 300/150.