just a shot from me: a shock coulb be bad or a strut mount. that is exactly the problem with my fuc**ng ford focus. it in the shop for oilchange and stuff and i had the same thing so i told the mech, to have a look. the strut mount is gone.....replacement.....aaahhhh with 16000 miles....i go mad.....damn ford cheap shit!
my bimmer has 60000 miles and still the first shocks!!!! not even those had to be replaced!!!!!