Join Date: Nov 2010
Location: Nicosia, Cyprus
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Assuming that you have Xenon lights, it could be the Xenon bulb itself or the ballast. Also, if you have a car with a sunroof, check for water ingress down to the FRM ECU which is located in the passenger side footwell.
If you have access to a BMW scan tool (not a generic one mind you), then you should check for errors on the FRM. The computers are capable of logging such intermittent errors.
I had a similar problem on my 07 R56, which disappeared after fixing the sunroof drains. Go figure...