American Bulldog Breathing Issue?

Our 8 month old ABD puppy started having trouble with his breathing. It doesn't happen all the time -- sometimes just when he gets excited. It sounds like a loud snorting fit, almost like he's choking on mucus. It resolves quickly, but it's kind of freaky. I've raised a Greyhound and a Boxer -- but I've never heard anything like this sound. Has anyone ever had an experience like this with their ABD or other breed?