It’s either your display or your GPU. There are a few ways simple ways you can isolate the issue on your own.
1) The next time it occurs, take a screen shot using the key combination shift+command+3. If the same distortion appears on your screenshot, then the problem is with your graphics processor and you to get your logic board replaced. If the distortion does not appear on the screenshot, then the issue is with your display and you need to get your display replaced.
2) Connect your machine to an external monitor (via HDMI or display port) - if you see the same problems occurring on the external display, then it’s your GPU. If not, then it’s your MBP display.
It’s also worth running Apple Diagnostics to see if any issue is detected. Hold D at the startup chime to run it. Just be aware that it’s prone to false negatives since it’s 1) running a test on itself and 2) not every component is tested. See the reference codes here.
Unfortunately, the bottom line is that this is indicative of a hardware issue. You’ll still need to bring the machine in for servicing after you isolate the problem. If you purchased AppleCare with the machine, you’re still in the three year window though. Best of luck.