Tighten the sway bar links. I had a similar issue hundreds of miles after a suspension rebuild. Using an impact is not enough. You need a hex socket and closed end wrench to tighten them. Plus, you have to have the correct load to find a loose one. I tried looking for the knock on level ground. Ended up using ramps and a good size crow bar to find one was loose.

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'06 X5 3.0i - bought @143,123 miles (12/26/20)