has this always happened in the same place on the autobahn?
if so, do you notice any microwave towers nearby. or any military antenna farms.
i used to experience a similar problem when driving near an antenna array. some strong radio frequencies were infiltrating the computer and glitching it.
if you suspect this could be your problem, you have a rfi/emi infiltration problem that can only be solved by better shielding your engine management computer.
alternatively, what are the weather conditions when you experience this problem. rain, perhaps. anyway, you might have a problem with a circuit board.
if either of these are your problems, you will need to grab the dist rep and take him for a ride into the area where you experience these problems. otherwise, it will never be soluble.