loss of power on Audi 100

I have an Audi 100 2.0E 1994 which is OK when started from cold and runs
well. But after a few miles, if I stop and switch off the engine, when I
return to the car after anything up to 3 hours later, although it starts
well enough, when I pull away it loses all power within about 100 yds. It
doesn't stall and if I push the clutch in and 'coax' the accelerator, it
picks up and then drives ok again. The whole episode lasts around 30 secs
max. A sensor problem? Any answers? thanks