stalling

What is your question?

my 2004 a8l starts fine after 30 seconds it stalls then can be restarted like nothing ever happened then repeats this process every 30 seconds at an idle or going down the road at any speed. if im going 50mph or above when it stalls i can mash the gas pedal and it will recover and go for another 30 seconds under 50mph i have to restart.