http://www.nikonchat.com/nikon-warranty-center/

Nikon D80, the strange noise?
Has anyone experienced a strange noise when camera shake (D80). I have owned for a little more than 2 months, and when I shake it, it sounds like there was a loose spring of some sort. Is very weak, but clearly evident. Has this happened to someone else or does anyone have any suggestions? Warranty? service center? Thank you very much!
Stop moving the camera! But yeah, that noise is probably normal. The D80 has a sensor inside to know when rotated to portrait orientation. Chances are that what you are hearing.