Screen Flickering and Distortions

as the title says, my game started flickering this morning for no reasons at all. ive been playing this game for a week now and i didnt encounter such problem. just now. what i meant by flickering is, some polygon-shaped figures and line appears, reappears and dissapears all over my screen. what to do?

Whenever something like this happens for any game, your first step would be to check to see if your GPU drivers have an update available and to check when the last driver update was. If a driver was installed since the last time you played and this happened, you have to rollback the driver. You also have to make sure there are no new Windows Updates.