Pink and green stripes on a laptop?

For a few days now, after starting up my laptop, I have always had pink and green stripes on the screen, but they always disappear after about a quarter of an hour. What could be the cause and how can it possibly be rectified?

Sounds like the soldering points on your graphics card. Cold, poor contact and streaks, warm better contact, no streaks

If it were a computer graphics card, I would have said take it out and put it in the oven. It gets a bit difficult with a laptop. As @ DerAmateur426 already said, this is due to cold solder joints.