Pomeranian having reverse sneezing/wheezing attacks, please help!

Hello all,
My 4 year old Pomeranian has been having these attacks of reverse sneezing/wheezing lately. I initially thought the house was dusty and vacuumed every corner, nook, and cranny. He still had them. After seeing them increase intensity one night (they don’t have any identifiable pattern), I worried he had an upper respiratory infection or tracheal collapse so I took him to the vet the next day. They did X-rays : no bronchitis, no tracheal collapse, no identifiable problems. They didn’t think it was allergies since he wasn’t scratching or sneezing or even coughing! They okayed 12.5 mg of Benadryl up to 3 x a day as needed.
Has anyone else had this sort of experience with their pup or know what it might be? Thanks! I’m attaching a video so that you can see what these attacks look like – they typically last a few minutes.