Could you try to do the following?
1. Reinstall your graphic drivers. (Perform a CLEAN installation) >> http://www.nvidia.com/download/driverResults.aspx/116344/en-us
2. Clean your PC. (Dust)
3. Try to run Speccy ( https://www.piriform.com/speccy/download
) when you're playing a videogame and see if anything is overheating.
*Step 1 is a Windows 10 driver. If you are not using Windows 10 then I can find you the right driver according to your Operating System.