I would really like to know if you found any answers. I have had the same problem for years. It feels like air is moving up the esophagus and wants to come out in a burp, but it gets stuck, and then seems to go back to the stomach. And it just goes round and round this way. About the only way I can get rid of it is to lie on my LEFT side and let it do its thing for a while. Eventually, the gas seems works its way through the intestines and comes out....well, the only other orafice it could come out of.
The part that I find disturbing, is that it seems to frequently cause heart arrhythmias until the pressure dissipates.
There is no pain associated with this, just bloating. I was diagnosed with GERD once, but then my next doc told me, No, couldn't be if there is no pain or burning. He said not to worry. BTW, I had an x-ray once that showed a bubble of air near the top of my stomach.
I'm interested in any info you received.