Mine does it as well. I initially started to get worried that it was the transmission, even though I've only got 17,xxx on it and it's very faint, but it also does it in park when I rev the engine.
Bracketron SI? That's what I use and it is similar, has a small magnet between the phone and case and holds my Note 4 securely. As small as the magnet is, it's surprisingly strong. It mounts on smooth and textured surfaces. I travel a lot for work and am always in and out of rentals and it's...
I have the exact same problem with my 2014 Trail. It would only happen above 40 MPH and sounded like it was coming from behind the gauges. After reading your post, I checked the mud shield clips and sure enough, the driver's side were loose. Shaking the mud shield produced the same sound I'd...