Desktop Screen turns OFF and ON for few seconds.

Hi !
I am using DELL VOSTRO 220s desktop computer with a Windows 10, 64 bits OS. Since last few weeks, the screen turns off for few seconds..(2 to 7 seconds).. and turns back ON. It happens intermittently and in random order. When it turns off, it is pitch black...just like a power off stage, and when it comes back on, it is just usual screen it was before. It responses the clicks, drags or any keyboard inputs during the turned off stage. But it is damn annoying like hell ! Also, it does not play any videos within the web page, but only audio. While it plays any Netflix movies and DVDs flawlessly.
Any Guidance? Any suggestions?
Please help.
Thank you.

Pat (SONYPAT)