94 Firebid vibration

I just bought a 94 Firebird with 27,000 mile (not a typo) It has a 3.4 V6 engine with Automatic Trans. When i'm stopped at a traffic light i feel a strong motor vibration, the engine runs fine but i'm sure it has not been tune in a while. My brother told me it could be a motor mount. Anybody expirienced this before?