I had an intermittent no start issue. Crank with no turnover. It always eventually started within 10 minutes or so. iDrive dash warnings would almost always show up after a failed start-- "No warning tones", Airbag, DSC, 4x4, etc. Occasionally a CEL too. I always just cleared all codes/warnings with my scanner and they'd stay off until the next time it happened. Sometimes a month, sometimes the next start attempt. I'm relatively confident it was the black terminal 30 relay in the rear electric box... The contacts were crusty and corroded inside the relay and the no start issue hasn't happened since I replaced it.

2010 X5D 115K miles
3rd row