Sometimes my laptop screen goes like this for no reason, the laptop is not overheating when that happens, that's for sure since I've measured it.
When I turn it off and on again the screen goes back to normal. What could be it?
Either the GPU is failing, the ribbon cable connecting the panel to the controller board is failing (or loose), or the ribbon connecting the controller to the motherboard is loose. You should look up a teardown video of your laptop, and try reseating and and all ribbon cables but particularly the one travelling through the hinge.
had a similar issue where the backlighting for my screen would turn off randomly and come back on when i restarted. took it to an it guy and he said it was faulty power wiring that was screwing with it. advised me it was cheaper to get a new laptop than to fix the old one.
That's what LCDs do when they were getting a signal but now aren't. First step is to split the laptop and dismantle the screen half, then put everything back together. If that doesn't sort it, you need a new ribbon cable.
Google "<your laptop> service manual", then follow the instructions for replacing the LCD panel. If you need a ribbon cable, hit up eBay. Make sure you get the right cable for the exact panel you're using. Photograph the cable while it's out; that'll make your life easier if you need to buy a replacement.
Then he's an idiot: all it needed was a teardown and a new ribbon cable.