Well it could be a few things. However, I must mention, if the laptop is under warranty still, then you should contact the manufacturer about any problems rather than do something to void the warranty.
That said, it could be a few things.
1. You can try updating the drivers and see if this helps.
2. You can open up the laptop and check the ribbon cable that connects the display to the laptop and make sure it isn't pinched, damaged, bent, loose, etc. If loose, then just reconnect it. If it is damaged in some way, then it would need to be replaced.
3. Next I would try turning the laptop off, connect an external monitor, turn on the external monitor and then turn on the laptop. Do you get the same issue on the external monitor? If no, then the laptops display is probably going to have to be replaced.
4. If the problem occurs on the external monitor as well, then your graphics card is probably the problem and will need to be replaced.