My yorkie is 2 years old now and he has done this noise since he was 5 months old. At first it scared me and now I am use to it. He will do it a few times a day and sometimes not for a week and then he is back to doing it everyday. I think he has a very sensative trachea. He chews and swallows everything. So when he has gotten into something he does it more often. My vets are not concerned. One told me acid reflux problems and another told me collapse trachea. This is what he sounds like when he does it.
https://youtu.be/iWA32rh7mfU I had a shih tzu too. He was the best dog He lived to be 16 how old was yours?