Driving the A6 hard yesterday evening. I had been playing with the ESP button. Can't remember if it was on or off. Took off from light, transmission in S. think it was at the 2-3 shift, near red line. Engine felt like it hit something. All kinds of lights lit up, including engine and ESC button. Car stumbled and I slowed down. Felt like I had lost a cylinder. Was running, idling like that. At first I thought I had blown one of the spark plugs out. Car ran like that until I got home about 5 minutes later. Somewhat shaken I waited until after dinner to check on it. Oil fine, no obvious damage. Coils all in correct place. Started it up and it ran fine. Today, I checked it again and ran it. It runs fine. What the heck did I do ? Did I somehow hit the rev limiter and it shut down a cylinder? Does it reset by itself? Any thoughts? 2008 A6 3.2

 

Did the CEL come on? Check/post codes.

 

I had that happen to me on my a6 2002 4.2 - driving hard in the upper RPM range, suddenly it started shaking and it felt like the car hit a wall (kind of). Some lights came on, etc.
Turns out my air filter cone came lose and unmetered air got into the engine pass the MAF. Once I reset the light and fixed the lose air filter it was golden ever since.

I just don't know if you had something similar happen or something entirely different.

edit:
reading codes would be a good start