Hi,
I just logged into this website again and saw your comment. I wonder if the iPhone still has this issue. If it does, then maybe this can solve the issue. I just realized that I watched a YouTube video yesterday and in the video he has this issue and it came out that the cable that's connected to the screen got loose and it's causing this static glitch on the screen. He fixed it by reconnecting the cable and it was able to power on properly. I hope this helps 😁. U would need to take it to a repair shop to have it checked it could be the issue.