My little girl has been doing this alot lately too. If he doesn't seem like he's stressed in any way or showing other symptoms of bloat, (lethargic, pooping significantly less or not at all, has a hard, extended stomach etc.) then he may just be becoming comfortable enough around you to stretch and rest in weird positions. If he's still acting normal otherwise, I wouldn't worry too much.
If you do think that it is more than that, try infant gas drops. I've heard those work wonders for chins.
Just doing a quick Google search on chinchilla bloat symptoms...
- Loss of appetite.
- Hard, swollen belly.
- Pressing belly against floor of her cage.
- Stretching out.
- Walking with “army crawl”
- Breathing rapidly.
- Standing with rear in the air.
- Rolling from side to side.
- Lying on side
- Stomach gurgling
- Sitting in hunched-over position
- Small feces, if produced at all
- Grinding teeth
- Reluctance to move