THANK YOU SO MUCH! What you said, I think you may have figured it out. Last year, I started grinding my teeth at night. I would wake up in the middle of the night because I would slam my teeth together, and started to develop TMJ pain. So, I had a custom night guard made, but then I found I would it would keep my lips slightly parted while I slept, which dried my mouth and throat while I slept. So, I bought a velcro anti-snoring head strap (https://www.amazon.com/gp/product/B081NJT3YF/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 but an older model) but in order for it to keep my mouth shut, I had to get it pretty snug, which I now think may have been pressing on my airway.
The last week or so, I've been only attaching it partially (the part on the front part of my jaw, and wearing a sleep mask to keep out light, which helps keep it from riding forward/backward and falling off my head, and I haven't had any significant episodes since. A little chest pain here and there, and a sensitivity to any form of anxiety or overstimulation (I think my body might just be in a very hypersensitive healing state right now to encourage rest, I was only getting about 4 hours of sleep during those episodes, and waking up several times a night).
I am waiting on old ECG's from 10+ years ago, so if it shows the taller P-Waves, I guess it might just normal for me, probably precipitated by the head- strap airway obstruction. I've always had chemical sensitivities that manifest as chest-tightness/shortness of breath. I've had many doctors since childhood tell me that I might be considered borderline asthmatic, but I am a minimalist when it comes to pharmaceutical interventions unless I cannot get around it with diet/exercise/lifestyle changes.
I will still go ahead with my doctors appointments for due diligence, but I think you have solved it and helped ease my anxiety enormously. Thank you again! : )