Since I don't yet have my CS, I'm not speaking from personal experience but with most new cars loaded with electronic nannies, it's not surprising to have audible clicks and buzzes. But it's disconcerting when happening for unknown reasons. To minimize parasitic current draw, the manual on my X3 recommends locking the car when parked. This apparently shuts down any unnecessary electrical activity. Expect certain things to still be alert but might be worth a try - or you may have already tried it. Just a thought . . .