Captain chair rattles

What is your question?

I just purchased this vehicle 3 wks ago. Had 12k miles on it and literally a day after purchasing it the Dr side captains chair started rattling and shaking like crazy. Even when my child is in it, it does it. I can't figure out why. I've moved it up and back and it still does it. The only time it doesn't is when it's folded down completely. The dealership wants 145.00 just to look at it.

What makes this problem better or worse?

Any type of bump

How long has your 2020 Buick Enclave had this problem?

3wks