This has just happened in the last few months. Sometimes it works fine, other times the screen flickers and goes off. I can usually bring it back on by gently tapping the edge or moving the screen. I suspect something is loose, but don't know how to fix. Afraid to open without guidance and can't really afford to take it to a computer store. I do have some computer tech friends I can take to if it should be done by a professional, but wanted to find out first what could be wrong.
Welcome to the Community.
Try connecting with the external monitor and see if it flickers.
Also run a Dell Diagnostic Test- by following this simple steps-
1. Turn off the Computer.
2.Hold Down the FN Key on the keyboard and press the power button, then Release both buttons.This should start a Diagnostics.
3.You will see two color bar screens appear in succession, on the second color bar screen there is a message asking you if you saw the color bars. Press the N key for No to start the LCD BIST.
4.The LCD BIST will run several full colored screens in succession with a beeping sound.
5.Check for any lines, distortions, or abnormalities you were seeing in the Operating System here.
6.Once the Diagnostics are finished you will see an Error message appear, this is Normal.
7.Press the N Key to end the Diagnostics or Press the Y Key to continue the PSA Diagnostics.
8.Check for any sysmptoms display.
Let me know if it helps,