I had an autoimmune disorder, Giant Cell Arteritis, which was not diagnosed for a while. Over a period of nine months, I had a number of gagging attacks, which were debilitating. They usually started at noon hour. I got a squiggly feeling behind my navel, nausea, sweating on the top of my head, then heaving. Would have to run to the bathroom. I would just keep gagging, dry heaves, and it felt like it was a straight line from my navel to my throat. The advice for vagus nerve attacks is to lie down flat and elevate the feet.
I started doing all kinds of exercises to retune my vagus nerve, humming, taking cold showers, etc (there's a lot on Google). Eventually, they went away, but they were hell. (Maybe the exercises to reset the vagus nerve worked).
I was diagnosed a couple of months after the last attack, went on Prednisone and have not had a recurrence, but it was strange. The gagging attacks are not listed as a symptom of Polymyalgia Rheumatica or Giant Cell Arteritis.
I hope you find some relief.