Sounds engine related. Check motor mounts, accsessory belts, tensioner, etc. Can you rev it in neutral and see if there is a vibration?
previous owner replaced motor mounts with poly mounts so engine does vibrate through car, but this is rotational vibration underneath,
Possibly, flywheel or torque converter? If when you rev it up vibration gets worse. Also check u-joints on driveshaft.