Thanks for the replies, I'll add this to my list of minor items to have the dealer check out (moonroof noise, etc). No, I don't have any aftermarket parts or upgraded electronics. This has only happened the one time in the 2+ months I've had the X3.

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2004 X3 2.5i: silver grey, steptronic, premium pkg, heated seats, xenon, gray leather
2002 Mini Cooper: black/white, premium pkg, sport pkg, cold pkg, black leather