I have heard this is a common ailment and my papillon does it regularly- it's like a coughing/choking sound as if something is stuck in his throat. He does it if he is excited or suddenly disturbed from a slumber, etc. Why is this a symptom with paps and not other dogs?
Laura

I'm afraid it does occur in other dogs and can signal a problem with the heart, I would have him checked out with the vet.

It can also be collapsing trachea which most toy dogs can get.

It can also be simply over excitement.  One of mine does it most often when she is eally scenting around, especially in the polen season and when the grass is long and flowering, so \i suspect she gets a nose ful of pollen along with deep scent.

If you cover his nose and mouth for a couple of seconds does he stop it?  this is what I do with my now 10 year old moocher!

I gently rub their throats and blow softly into their nose and talk softly they calm down.