What the hell is this noise? (E60 BMW N47)

https://reddit.com/link/1uodhgh/video/c3mo4p3w6hbh1/player

My 2010 E60 is making this faint almost 'wobbly' noise. It's only noticeable at low RPM in 1st and 2nd gear, no noise at all when revving in neutral.
Any ideas/