So for anyone on this thread/who had this problem, I JUST realized I have this on my PASSENGER side seat. Ironically, I only found it out when my Model 3 had a sound problem after a screen black-out and I was driving in silence for awhile before I figured out how to restore the sound with a Power Off move on the screen settings.
When I accelerate and decelerate, even a little bit, the passenger side seat totally squeaks. It's not noticeable unless it's absolutely quiet/no radio, but it's pretty annoying and kind...Cheap sounding, for lack of a better term. I took delivery 12/30/18, so it's been almost 7 months, and I'm due for a complimentary tire rotation change (I think this is included at the service center after 5000 miles driven, is that still true?), so maybe I can ask them about fixing the seat also? At first I thought it might be the interior paneling on the passenger side, but it seems to be the seat if I listen closely.
I have unfortunately a laundry list of other minor but annoying complaints that I have to tell them about (Gear Shift casing that says "P D R N" etc is not flush & starting to peel off, The screen has reset 3-4 times and gone blank sometimes while driving which is scary, Rear Camera occasionally goes blank while reversing, Radar seems to have very jumpy animations for nearby cars which seems like a camera calibration problem and makes my Autopilot go crazy sometimes, etc)...I'm wondering if I should tell them about it all at the same time?
Other than that, I really really love my Model 3, but sometimes I just feel like I'm driving a very buggy iPhone that keeps having software problems!