Computer screen goes blank for a min than continues

[Hadenough]

Hello,
computer screen goes blank for a min than continues" Here and there. Often when I post or starting to watch a video . It freezes at that time than in a min it's okay

 

[Cyberat_88]

Check your video card temps. or your cpu temps, respective apps. cpu-z and gpu-z free to download.
Is your system overclocked ?