Strange choking sound

Our Pepper (15 weeks old) seems to make a strange sound. I noticed it once while playing fetch & being very active for a long period of time, he suddenly started making this reminded me of a human asthma attack. It appeared as though he had something caught in his throat or that he was going to vomit (neither of which was the case). He made this same sound again today & I have no idea why he does this. Any thoughts?

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