Question Laptop screen randomly goes black on start up and turns good after some restarts or by itself

[AbdulHadi1]

My laptop screen goes black at start up nothing shows on the screen but a white backlight on the display shows and all keyboard lights are working. After some restarts and some time automatically screen turns on and everything shows up. Then while I'm using the laptop suddenly screen flickers and there are lines all over the screen and nothing shows (but it's not black lines). Previously these lines go away on their own without doing anything. but now these lines don't go and when I restart the laptop, again on start-up black screen shows and the whole process repeats.

Note: Black screen only comes on start up and It won't go easily and after some time or maybe some restarts idk, this black screen turns back to normal.
The colorful (Rainbow type + white) lines come while I'm using laptop and windows is logged in and I'm working(Not on startup).

Can anyone guide me on how to resolve this issue.?

I have checked Ram It's good and also tried pressing the power button for 10 to 15 sec and all those tutorials but nothing helped.