Same to you. So sorry that's happening, but at least its not your heart. :)
I wish I had an answer for you.
Three months ago, while super-relaxed, sitting my couch, I suddenly felt as though I was losing consciousness, my heart started pounding (but not racing), my vision went blurry, I felt like I wasn't getting enough oxygen (but not shortness of breath), muscle trembling, whole body shivering, nausea, and diarrhea.
It lasted just a few minutes.
I went to a walk-in clinic right away, but my vitals all tested normal and, by then, my symptoms were greatly lessened (coming in decreasing waves, the rest of the day). I was told it was too vague to diagnose with a physical exam.
The 3rd episode (and worst to date, at that point) landed me in the ER. It took 2 more ER visits before a doctor actually considered a possible cause, rather than just dismissing me. That doctor thought "heart".
Alas, all my tests, includng heart monitors and echo. have come back normal. So, now the theory-du-jour is that I may be experiencing severe hormonal imbalance reated to perimenopause. I am almost 50. I have no idea if that's the cause, partly because my periods are as regular as clockwork, and I have never had a hot flash or night sweats.
For now, I'm in wait'n'see mode.
Best of luck with your diagnosis.
It could be the acid reflux or an esophagus problem.