Pink bars screen on MacBook Pro 15" 2018. Trying to start in recovery mode with external screen - Lemmy.World

I’m trying to wipe and reinstall my old MacBook Pro that has the funny pink/green/grey bars on the screen. I’ve tried to hook it up to my tv and it worked once but when I had to reboot it I can’t get the image back to the TV. Is there any tricks except physically disconnect the built in screen from the motherboard? I’m trying to get the command-R start to start it in recovery mode but all my TV is showing is “No signal”.