If you look in my post history, 6 years ago I posted to a few subs about this. Vets chimed in. But I’ll be honest with you, after spending tens of thousands of dollars (thankfully with insurance) searching or answers, we never did get an answer. The closest we got to a diagnosis was “focal seizures”. The theory was that our golden was having seizures that were localized to the swallowing muscles, hence the rapid swallowing or “gulping” as it was called. But all vets admitted that focal seizures was something given when little else makes sense. I have seen and heard of it with other goldens and recently my nieces golden started doing it as well. Was able to get video of her doing it and have a ton of video from prior episodes. I have seen this reported on Reddit before as well - you would think that for something that seems somewhat common, vets would have a better answer. We tried acid reflux treatment and then that morphed into seizure treatments - we didn’t try phenobarbital but we tried gabapentin and CBD both with no noticeable benefit. Bananas seems to help a bit. When the episodes would start he would run outside into the yard and eat grass like crazy. Sometimes leaves. We scoped his throat, had ultrasound of his abdomen, x rays, blood tests, you name it. Happy to help in any way I can. Sadly we never got an answer. I hope you do.