OMG Fay's starter

[suffolkd at aol.com]

Fay:

When cold, the electrical contacts can be close enough to work and not when its warm.

I ran through this on a Ford, drove me crazy because it was intermittent.? Solenoid on the fender.
replaced starter, ignition switch, solenoid, etc................? Big $ drain.

You seem to have two items to focus on:
Starter and the little exciter wire which corrodes.
Ignition switch.? <-------check if you get other weird things happening during start up/turning the key.

I'd check the alt/battery output so you don't get stranded in the winter too.
The auto zone battery brand tested tops in consumer reports a few years ago.
I have one in our 99 A6 Avant ~$60

HTH 
-Scott by BOSTON