Dell Latitude 3500 screen problems

Hello,

A few months I started having this problem with my screen that it'll go completely black with some blocks that keep flashing all over. This won't stop until I hold the off-button for longer than a minute to shut the system down. The screen doing this occurs mostly when I move the laptop but sometimes it'll also do this without me moving it, but it does trigger it more.

I tried looking for updates, I tried deleting software to re-download it but nothing has helped and I wanted to troubleshoot here before having to pack it up to send it in for maintenance in case it is something very simple.

Please help me! Thank you in advance.