It sounds like it could be respiratory. Maybe stress, has anything changed environment wise? (like moved furniture, moved the cage to another room, separated the brothers). If its been happening for more than a day or two, even if he's acting okay I'd call a vet. Chinchillas are very talented in hiding illnesses and weakness; meaning first signs are sometimes the only signs. If you do go and it's nothing, at least your conscience will be cleared and you can always work extra hours or cut back in some other area for money. Better to be safe than sorry.
Before I got a chin, I first got a horse a few years ago. From their big bills (my friend payed about 400 bucks to get a woodchip the size of your pinky nail out from her horse's hoof) I've learned to just always have a rainy day account for just in case. Its a simple and good idea
Hope your boy is okay!
