my 540 was doing the same thing. happened twice in a month where I pushed the start button and it sounded like it was about to crank, then didnt. I thought I was pulling my foot off the brake too soon..but at my oil change I had them look at it (and my parking sensor).
They found the starter was going bad, so they replaced it and the parking censor.
the extra CPO I got paid for itself that day
