During those times does your ribcage and chest feel very tight and restricted?

Do you feel like it could be from severe spasms in the neck, chest and upperback?

Many years ago there were quite a few posts about some that went to ER thinking a heart attack, and nothing heart related was found.

I had a bad bout for awhile years ago, where those muscles were in severe spasms. I felt like I had to cough, and could feel my heart beating/vibrating.
Luckily a few days into it I happened to meet a chiropractor that could tell I was in major spasms, I had no clue that was the problem at the time).

I made an appt with him and he used many PT type modalities to resolve the spasms as well as some adjusting. Ultrasound, E stim, low level laser, Nimmo/trigger point work, etc.

Also found out later on, that my top ribs had gotten pulled up and were stuck in the raised position and that was causing ongoing limits to my arm use due to the added compression between top rib & clavicle.
Got the ribs dropped down and it was so amazing the difference. This was discovered by an advance PT person in a 1 time evaluation visit.

They did slightly pop up at times later on but then I could tell what it was and mentioned it to chiro and he would check for it regularly after that.

If your muscles feel rock solid when compared to another person's same muscles, those are spasms.