[LunarBerry]

I'm thinking it's either a trachea issue or something a bit more minor like allergies or they just tend to get thing caught in their throats. I get this way all the time at work because of hairs, dust and products, etc. Yorkies are so low to the ground, it don't surprise me they sniff up more stuff that messed with their sinus/throats. My girl honks/oinks and snorts often. I've once been told it could be because her nasal cavity/area is small or allergies.
We used to have a male yorkie that did it too but he had allergies, as well.