I had this problem on my old Lumia 900. I had a white one, sold it, and bought a blue one, and now I haven't had the problem since. One thing I've noticed is the vibration and screens seem different (screen had more of a yellow tint on my old 900) and the vibration is much stronger (to where I can actually notice it in my pocket now lol).
I think some just have defective parts and screens, as another annoying thing that would happen is if I pressed the back button it would register as a long press ALL THE TIME. It got really annoying, which led to me selling it and finding one that didn't have these issues (plus I like the blue better than the white one).