Like mugsy said, it may be reverse sneezing. If it's reverse sneezing...it'll sound like he's trying to breath really hard and almost gasping for air for a little while. It sounds scary but it's usually nothing serious. Kai has that and still has the occasional "attack". The vet said it could be allergies or even something more serious like an item blocking a path. The vet told us that most of the time, it's nothing serious but it's wise to check anyways.