High miles for an M278 engine; the vibration could be misfires on a couple cylinders as for bore cylinder scoring is common on these if they were maintained with oil change intervals every 10k miles. Really should be every 5k-7k miles depending on drive style.
It's a shame to see these nice luxury cars start to enter the phase of people not loving them so much anymore. That used to someone's pride and joy and now it looks like it gets run hard and put away wet lol
