So I have had this laptop for over a year, and recently the screen on it starts flickering and glitching whenever I try to move it. It shows that it is trying to output something but its virtually impossible to tell what it is. I connected it to an external screen and that screen is fine.
Sounds like either the attached display is going or the cable that connects it is loose or going itself.
You will need to open it up, if you feel comfortable doing it yourself, and I would start with the cable that connects the display. If you can carefully disconnect it at both ends and then reconnect it. If it was loose that may solve the problem.