There are a few options here:
- Display is physically damaged
- Video memory is dying
- Video connector is damaged
- Memory faulted in sleep mode
The first option can be verified by turning your laptop off and look for cracks. Another option is to carefully tap/push on a side of the display (also the display itself) and look if it starts acting weird, you should not push too hard for obvious reasons (clean fingers may help too :)).
The second option can be verified by a memory check and a video memory check. There are lots of programs for that on the internet. If your OS comes with a memory tool, use that.
The third option can be checked by slowly turning your screen fully open and look for when it starts to flicker or crack.
The last option is the easiest one to solve. Just execute a clean reboot and all should be fine again.
If there is any physical damage you can take it back to the store if you like.