That is called Artifacts.
Those can appear due to Defective GPU, Overheating, Overclocking, PSU Power issues, Some times the Graphics driver.
If those artifact occurs all the time even when booting up then most like your GPU card is going bad.
Try stress testing the GPU card and see if those artifact occurs or it fails the stress test.
Download and run OCCT PSU and GPU Stress test and also MEMTEST for the GPU and see if it passes or fails or the artifacts occurs.