I had an S too that would not start sometimes. The Building I lived at had to Valet my car and for every trip my car was started 4 times since they would start it and then park in the front of the building for me. It wore out my starter. They replaced my starter and then it was fine, but it is like you said, sometimes it would not start and I could not get it to replicate at the dealer. I am not saying this is your problem, but make sure that the alarm system is not locking out the starter and if it isn't then it is likely your starter. If you have a different key give that a try, the key has a transponder in it, also when it does it again try engaging the alarm and dis-engaging it to see if that will allow the starter to engage. Good luck!
Brian

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Brian W. Heitman

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