It could be more serious which is why it's best to have the vet check but it sounds like a fairly common phenomenon called reverse sneezing which actually has nothing to do with sneezing but is an irritation of the soft palette. I would have my vet check it out to be sure, but if you choose to wait until your next regular exam be sure to mention it as it can occasionally indicate a problem though most of the time there really isn't a physical reason. It is more common in small dogs and some breeds tend to be more prone to it than others. I found a video of a reverse sneeze for you so you have a better idea. www.petplace.com
