[DCinVA]

I have no definitive answer here, but perhaps I can be of some help.

Based on your description it could be lots of things. The good news is that it does it while parked in the driveway. Suggest you take off the engine cover, start up the engine, and when it starts making the noise look around to see if something is loose and vibrating. Hopefully something is coming loose and can be tightened up.

Good luck.

By the way, any additional information you can provide would be helpful in diagnosing the problem. Such as, It only does it when idling, never at speed, only when in neutral, stops when I push the clutch in, or whatever.