Need some advice from the E53 owners...

[Effduration]

I see from another post of yours, that you have an '06 X5 3.0 w/76k miles and you have owned this since April 2021.

Give your descriptions, I don't think you typically own a car, any car, very long.
If that's true, you should probably sell this one and move on.

BTW, It wasn't clear to me which car you were towing with where "you felt every jerk of the trailer". But whatever it was, check the size of your tow ball and the size of the trailer coupler. What you describe sounds like towing a 2-inch trailer coupler with a 1 7/8" ball on your trailer hitch.