@Former-Member I know exactly what you are talking about. Maybe it is because I too am a PTSD sufferer but I know what you are saying.
There is a thread on here, and every time I post on it, until I successfully push the name of it out of my head I have this totally irrational visceral response. My heart almost beats out of my chest, I literally begin to shake, I feel short of breath and I feel that draw of the black depths pulling back into it. I have to consciously calm myself with "affirmations" and reassurance and rationality.
I cannot control this. The first time it happened when I saw the name of the post I didn't even understand why it was happening, why I had been triggered. I reached into my mind to try to understand it and then I realised. It wasn't even something I had considered. But then once I identified what the subconscious connection was, and after being totally surprised it was the "trigger".. I was slowly able to start controlling it. I did not enter that thread that night or for a few days afterwards. It was nothing to do with the content, the title alone triggered it.
I can now go to that thread but the first 15 or so mins I am there, while I push out the irrational response and think through it, I still get that same response.
I am a very rational person. I am an "in your head" type of thinker, yet still I have the types of responses you describe. It is PTSD related, there is no doubt about it. It is physiological and it is neurological.
The way I am trying to control mine is through neuroplasticity. I learnt about a Canadian PhD researcher who is proving its validity and I use that process. I did use it even before finding her and because it started working for me is why I researched it and found her. Not the other way around.
It's horrible, it's mysterious.. but it is very real and I suffer from it too.