We've caught Andie resting this way several times lately. Head and front legs in the tube with the rest of his body in a sitting position on top of his house.
We are new chinchilla owners so we find so many cute things about him!
Haha my chins do EXACTLY this same pose as well. It's funny too because We had Buddha for about 6 months before getting our second chin Moose, and Buddha never did this until Moose came along and taught him how. Now they both do it. haha! so silly.