I wish I had some advice for you but don't. But my10 1/2 year old collie seems to do this as well. It's gone on for a couple of years. She'll gag and kinda make a choking sound like she's got a hairball or something but nothing comes up and she seems fine. It happens like once a day maybe twice. I asked the vet and they said everything seems fine with her but I do worry about it sometimes. Hope someone else has some better insight.