What is your graphics card?

I've seen this before on various gpus when I tried to overclock the card.
It doesn't mean that I'm saying you're overclocking, but it could be overheating in some way.

Does it do this when you first turn on your PC and hop on? Or does it seem to get worse as you're on awhile?
I'd recommend, depending on your GPU, to grab MSI Afterburner. It'll let you monitor temp and alter the fan speed to cool it better.

I'm pretty sure this is the result of the GPUs memory, possibly caused by overheating. Seen this a hundred times in my day.