I have a 95 VW Corrado VR6. The indications are that the vehicle will turn over and increase RPM when ignition is turned over. When RPM goes down to idle it continues to zero and dies. If I press the accelerator while starting the car the same thing happens. This originally happened back in October and I did not get it fix or looked at until early April. The shop I took it to replaced the battery and it started right up. I then drove it off and on for about 3 weeks (low speed/no freeway and no more than 1 hour in duration) and then it started doing the exact same thing. That day I had driven home from work which is only about 3 miles. Several hours later I needed to move the car and it started and I moved it 40 feet or so. I then decided I didn’t like my parking job and tried to start the car again and it would not start. I am thinking a faulty alternator but not sure if it would fail like this.
I had this same problem with my Corrado. It sounds like you have some weak ground connections in your electrical system. To fix it I replaced the positive and negative battery cables, cleaned the battery terminals, and cleaned every connection to ground I could find. I also replaced my spark plug wires under the assumption that if all of my other wires are corroding those probably have as well. The car has run fantastic for me since then. If you don’t want to spend anything just clean the battery terminals and ground connections and it should run much better. Good luck and I hope it works as well for you as it did for me.