In the last three days I have been having a hard start issue on my '06 R500 w/ 53k miles. First thing in the morning it will not start on the first crank. The starter goes but the engine doesn't start. The second attempt always starts the car. I tried both keys [keyless go] and it does not make a difference. It only happens after the car has sat for a long period of time and it so far has always caught on the second attempt. I searched the archives and haven't found any similar posts. The car has been totally reliable otherwise and maintenance is all current...

 

I had a similar problem with a VW Passat. It turned out that fuel line check-valve was broken and was letting fuel pressure to drop and it required a second attempt to get it working.

I would take it to a mechanic, leave it overnight and have them figure this out.