strange noise coming from near Fuse box on '06 M35

[RyanD]

Guys,

While I had the car in the driveway, parked and running (in order to try to fix my bluetooth issue) I started hearing a low grinding noise, but it did not sound like metal on metal. At first, I just thought it was the nav DVD drive because it was muted and non-metallic. I popped the hood, removed the cover near the battery, and pretty much narrowed it down to where the fuse box is. By the time I could get a flashlight, it stopped. It did it pretty consistently before and after the car was warmed up. I am not sure if I can recreate it, it just started, and I certainly have not heard it under load. Any help would be appreciated

Car is an '06 M35 sport, 67K miles, dealer serviced its entire life.

Thanks,Ryan