I have a 2003 SMG M3 and im having the same problem. It's been happening for a little over a year now. It will start fine and then the next time I go to start the car it won't even turn over.
There definitely is some strange noise - much like gargling and it sounds like a computer or electrical current is sending a signal. I too have a fairly new battery. I replaced the starter as well but to no avail. I dropped it off at a dealer where they ran diagnostics and found a switch that was supposedly worn out and the source of the problem. After taking the car home that day, it refused to start once again later on that afternoon.
One thing I noticed is that the battery light flickers randomly and its most likely due to a failing alternator. I should have news from my mechanic by this weekend.
Thursday, April 9th, 2009 AT 10:22 PM