Ive had this happen to me last year and this year and believe it or not, its the change of season I think. This happened to me both times around the spring. Kind of works the same way as like in the winter when you hear a lot more rattles and creaking.
For me its when the weather or the interior gets warm. If i get stuck in traffic for a long time or hot summers day driving after 15-20 mins it will start to feel sticky and makes that squeaking noise. Annoying the hell out of me