The interesting thing about this case is that the two pictures you posted show the lines in differend orientation. One is vertical and the other is horizontal. Now there are two possible problems that I can think of that could lead to something like this. Mostly depending on what makes the screen do this.

If the creen does this randomly due to no physical contact or possibility of thermal expansion, then it is most likely your drivers. If you are running windows, then open device manager and uninstall all drivers for your GPU (or GPUs if you have both integrated and dedicated,) uninstall it for the screen too, then get the windows update to reinstall them.

Now if your creen does this when you physically move it, then it might be the case that the flat cables around your LCD came loose. In your case I doubt it would be the case as it is unusual for both Y and X to come loose and more unusual to only do it interchangeably. But it is a possibility. I wouldn't rush opening it up tho. Your problem is most likely software related.

What you can also do is to boot up to a different OS install from an USB drive (pendrive or external SSD/HDD) and see if the problem presists. If you have multiple GPUs in your system, then you can also try to disable them individually and see if the problem presists with only using the other one for a while, so you may narrow down source of the problem.

If nothing helps, a clean windows install might solve the problem.