Audi acceleration problems

I have a 1991 Audi 100, 5 cylinder, sedan. Starts well, idles fine, goes down the road with no problem. When I come to a stop after traveling and go to re-accelerate, I get a brief (0.2 sec) standard acceleration followed by a total loss of power for up to two seconds when it seems the engine is starved for fuel (putt-putt, sputter sputter), then everything catches and I accelereate like normal. I also get a reaction (infrequently) when I acclerate from speed. Say I'm goin 40 and step on it to get up to 60. I get what feels like a normal accleration response, then around 50 (this varies) I can feel the added acceleration as I press further into the seat. Suggestions as to a central source of the problem?