Two problems related to transmission not engage have been reported for the 2010 Audi S4. The most recently reported issues are listed below.
Vehicle was at a stop at a traffic light with brake engaged and vehicle suddenly engaged into gear and tried to surge forward. Had to put the transmission into neutral to disengage gear. In other instances, vehicle will slam into gear abruptly when accelerating from a full stop, and also lunges forward unpredictably. These incidents are all related to a failing automatic dsg transmission.
The dsg transmission is very jerky in 1-2 gears it operates as though the clutch is not engaging/disengaging properly. When traveling at highway speeds with the cruise control engaged the engine rpms wander as though the clutch is engaging and disengaging. Starting from a deadstop or driving at low speeds are very uncomfortable due to the jerky-ness.