iPhone screen flickers after about 5 minutes of using it

My iPhone screen flickers after about five minutes of using it, then I have to leave it for about 5 to 6 hours so that I can use it without a flickering screen.

I can provide a video if you want.

- I've tried all the software solutions. I have restored it, lowered the brightness and disabled auto-brightness,, but none of these solutions has worked.

Is it a screen problem or something else ?

-Thanks!