My factory radio went dim yesterday but then was back on when I restarted..

I started it up in the morning while we were on a hockey trip to Davenport, IA and the music and all functions were there but the screen was blank. I turned it off and on but nothing helped. I was thinking I had inadvertantly touched something but wasn't sure. Anyway, I came back out from hockey arena and was going to hook up the laptop to the cell phone and get on here and post about it but when I started the engine it was back on. Nothing like it since. Did I touch something or is it on its way out?
 
It's the factory radio with rear DVD and XM. 2007 Tahoe.
 
Thanks... G..

I had an occurrence where I had no sounds from anything.  After sitting for about eight hours and restarting, it was OK.

You didn't have the lights on did you?
In certain conditions the Autolamps can activate and if the small IP dimmer knob is in a dim setting the radio display will appear very dim in daylight.

The Autolamps can activate in the daytime in the early and late twighlight hours when the sun is not overhead or if you are parked in a garage or under some shade.