Hi, I have an issue with my audi. It just shuts off after driving for a few minutes (5-15 minuetes). Even if im just parked and running the engine, it just shuts off by itself after some time. It takes me a few tries to turn it back on, and again after a few minutes it will just shut itself down.

The car is a 1997 Audi A4 1.8L Quattro

Recently i took it to the mechanic to replace some spark plugs and ignition coils.($595 total) For two days the car ran EXCELLENT but on the third day it started the shutting off problem. The night before this problem started i left my headlights on for 4 or 5 hours...but that same night the car ran fine and did not shut off. The next day when i was driving it to the gym it started the shutting off issue.

So i took it to the same mechanics that replaced the ignition coils and spark plugs a few days ago and they said they could not figure out what was the problem.

My question is:
1. Do you think leaving my headlights on for 4 or 5 hours caused this problem?
2. Do you think the recent spark plug change and ignition coil replacement caused this problem. (by the way i took my car to a 76, not an audi dealer/specialist or anything)

If anyone can help me out here i'd really be greatful.