Screen shows black/gray/white stripes

Sometimes when I go around and look at something, black/gray/white stripes turn up on the screen, pointing at the crosshair. When I turn around, there are away. But when I look again in the direction, it happens again. This was also in the version 20w14a, but now it is again. Now I can stop that from happening by pressing F3+A, but they can appear again some time later.