It's not the Auto focus mech because I can turn on the camera and focus all over the place while tapping on it and it still does it.
Besides, I thought that was all digital focus?
It is the little metal contacts inside the headphone jack that rattle slightly whan tapped or shaken. It took me about a 1/2 hour one night trying to find where it was coming from. Plug a headphone jack in and it is gone!!! I stuck a tiny zip tie in the jack the evening I was trying to nail it down and just doing that stopped it.