Macallan21

I have a 2009 A4 P+.

I got in the car the other evening, and the MMI screen didn't turn on. Holding the volume/power button didn't work. All of the buttons around the MMI controls didn't work. No bluetooth, radio, nada.
I turned the car off and back on, still nothing.

The next morning the MMI all worked like normal. I looked around in the trunk at the head units but I didn't see anything obviously loose or damaged.

Any ideas or suggestions on what to look at next?

snagitseven

You may have experienced what is known as a one off "Audi anomaly".
If it happens again, try rebootiing the MMI (simultaneously press Menu (or Setup) + center controller + upper right function button). If that doesn't work and you have access to a Vag-Com, run a scan for faults and post the fault codes here. Otherwise, head to your service dept.