I just noticed the exact same sound as the videos before so I'm hoping it's just a pebble. Only happens at low speeds with or without the clutch engaged.
I'll try to give it a spin to see if it goes away, if not then I guess I'll take it to Seattle BMW.
I'm fairly unfamiliar with the car so I'm not sure how everything looks. Is there a link anyone can recommend where it shows the wheel/brake components, to know where to look for the pebble??