Why does my 3DS screen glitch out every so offen?
It will flicker black a few times than back to the game I was playing
Nintendo handheld device released February 2011, identified by model number CTR-001.
Which screen is glitching out?
It's most likely a loose connection or a dying cable. Try taking it apart and putting it back together. If that doesn't fix it, look into a new display data cable.
Here are instructions for opening it up. It's tedious but you can do it!