SOS! Mysterious problem..

[polly@svn.net, davepet@gnn.com (Dave Bisneth Neeran)]

hi all, 
I got a '92 AUDI 100 CS Quattro with a very strange
and unsolvable (??) problem. It could not start, 
carried to the dealer, put a new battery. Worked for a day, 
could nor start the next day!!! The dealer looked at it, 
replaced a window relay, said nothing is wrong. That was
in New Jersey. Recently relocated to CA, had the car shipped.
First day, fine... the next day !!! Cannot start again!!
Carried to dealer, they found nothing wrong, but they 
washed it... this problem comes and goes, always
overnight; if the car has started in the morning, there's 
no problem during the day. However, there are problems starting
it on some days. Any suggestions, advice welcome, most
welcome cos 2 dealers in each coast can't solve it!! 

Regards
Polly