I had an autoimmune disorder, Giant Cell Arteritis, (GCA) which was not diagnosed for over a year. Over a period of a few months, I had 29 gagging attacks. Usually, they started at lunch time, I'd get a squiggly feeling behind my navel, the top of my head got very hot, then I would gag and get dry heaves. I also usually had diarrhea.
A doctor friend told me I probably was having vagus nerve attacks.
One of the solutions to a vagus nerve attack is to lie flat with feet elevated. If I heaved a lot, I was exhausted and debilitated for the day.
There are a number of people online offering exercises to reset the Vagus nerve. I did these a lot. I also read Dr. Stephen Porges book, about the Polyvagal Theory, which he developed. He is a Psychologist and Neuroscientist. You can find information about his theory and interviews with him online. here's a link:
https://www.polyvagalinstitute.org/whatispolyvagaltheory
After a while the attacks subsided and I was treated for the GCA with steroids. The attacks stopped and have not returned, but they were horrible. I've never seen them listed as a symptom for GCA either.
Good luck. I hope you can get some relief.