If the hypothesis of a non-satisfactory ATP production applies to you, then this is the moment of energy production decompensation. It causes the feeling of a sudden and unexplainable "halt" in consciousness/breathing/muscle activity, after that you become very alert and subconsciously start racing the heart/lungs, feeling that you are not ok. Some people even feel that they may pretty much die.
But the exact manifestation varies from person to person. An example of a real-world situation is presented in [1].
> It makes me breath way deeper, but frequency seems the same.
This also counts as hyperventilation. It's either frequency increase, deepness increase, or both.
[1] https://news.ycombinator.com/item?id=29139740
P.S. I will monitor this thread from time to time in the following months. Just drop a reply if I can be of further help.
In the initial stages, attacks do occur mainly under the mental/physical load. The condition slowly but steadily progresses to everyday attacks over several weeks/months.
In the later stages, attacks may even occur during the night when a person sleeps or tries to sleep. A person may have several attacks during the day at this point.
> Do you feel pain when this happens?
No, just weird unpleasant "squeeze" sensation in chest.
> Does your breathing rate increase? (hyperventilation)
Not sure but probably not. It makes me breath way deeper, but frequency seems the same.