I have a similar problem with my 1997 Tercel. The vibration is in the steering column but it rattles things on the dash and shakes the cup holder and any drinks in it. I can hear rattling in the engine compartment when I'm sitting in the cab (when I'm stopped at a red light for example). The vibration seems to go away once I step on the gas though. One mechanic placed padding around the engine mounts (from what I can recollect, this was three years ago) and this helped for a while but the rattling and vibration are back. Unfortunately, I can't take my car back to that mechanic as he is retired now.