Sometimes I get a little vibration in the mirror when I turn the radio to max volume. Other than that, it is stable. Do you have the standard or auto dimming rearview? If you have an SR5 or Sport, the previous owner could have installed an auto dimming mirror and not fastened it correctly.
its a 2006 sport, nope its the normal one, and it shakes ALL the time.....not sure what could be causing that...