I have a 2016 Limited that I just took delivery of 3 weeks ago, 650 miles on it right now.
The temp in Pittsburgh just dropped like a rock (from 70 to 20) and I found this squeak yesterday morning. It sounded like a 1970s stationwagon going over bumps, I thought a bracket broke in the seat. The sound would go away once the temperature increased in the truck. I had the seat heater on setting 2.
It was cold again (25F) this morning, I set the seat heater to setting 1 this time. This time the sound appeared but just briefly before disappearing. I believe the sound was less severe because the thermal expansion was not occurring as quickly this time, so everything had a chance to re-expand together.
Due to that, its very easy to tell that (as mentioned above), this is a thermal expansion problem. Mine is coming from the right side, and when I move my back on the backrest or hit a bump, I can make it squeak (but only during the time when squeaking is normal). I will have to take a look one evening, but pinpointing this in the spring is going to be difficult. I might be stuck waiting till next fall for a time in which I can readily recreate the sound so either I can find it, or let the dealership putzs have a go at it.
However, won't lie, glad to see I'm not the only person deal with this.