It is most likely what is called a reverse sneeze. This takes most owners by surprise when they first hear it, as it sounds much more closely related to either choking or gagging than any form of sneezing. But reverse sneezing is normal and more common in puppies when they are growing, with one theory being that because they have yet to grow into their lungs, this occurs. It is also more common in brachycephalic breeds (those with short muzzles, like a puggle!). I've included a link here to explain about reverse sneezing:
Keep in mind, it sounds like loud snorting, looks like choking or gasping for breath. Often the body shakes with each one produced, and even after if it takes the dog by surprise. As long as your dog's gums and tongue stay pinkish (not bluish) he is able to get oxygen and can breathe ok, this shouldn't be an emergency.
Hope this helps.