Thanks for the tip. My elder son has been going through this with his 2002 A4. I didn't know about the 7-second rule, but he may have been doing that subconsciously.This is classic Crank Position Sensor (ESS) failure behavior. It doesn't die, it just gets flaky. Replace it.
If you have a crank/no start again, try this: crank for 7 seconds continuously. If the ESS wasn't giving a signal, the ECM will go in to a limp mode after 5-6 seconds and go ahead and start without the ESS. The EPC light will be on and the idle will be higher than usual, but it will run and drive ok. Much better than being stranded.
Anyway, I bought him an ESS, and this morning he and his brother finally got around to installing it. Their advice for an AMB 1.8T is to drive up on the ramps and have one person under the car and one above it while threading the ESS lead down from the plug-in point under the coolant recovery tank. They were done with the remove-and-replace in less than 30 minutes.