u/Fuckyoursadface

Bought my car recently, 18K miles, full BMW service history. Overall very happy with it, but I noticed when I drive on low revs (specifically between 12-15 mph) I hear this noise seen in the video. I also notice it at around 30MPH.

Interestingly, the more I drive, it goes away and eventually I can't replicate it at all. It's worth noting my battery was 0% the times I heard this noise.

Any help or advice would be greatly appreciated guys.