[naz]

something's up.. car shouldn't do that.

i'm gonna toss out some ideas:

are you using clip on or stick on wheel weights.. if stick on.. are you sure they are still in the same place as where they should be?

take your rear tires and put em up front.. does it still happen? maybe one of the tires is just messed up

is the vibration when you are on the gas or on the brake? if brake, your rotors need to be resurfaced (i had the exact same thing happen)

put the car up on jackstands and have a buddy grab the tire and try to move it around while you are underneath.. see if anything is moving around underneath.. check all the places where the suspension components are bolted together