Does it only occur when it rains? We had a serious air conditioner leak in our 1yr old E70. We found it after the car died in the middle of the street. It turns out that the leak had been present for some time and ended up corroding some electrical components. We never actually saw or felt any water but the service guys noticed it and traced it to the air conditioner.

Obviously you can disregard this if it only happens after it rains.