> 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.
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?
> then I have problems breathing normally
Does your breathing rate increase? (hyperventilation)
Next time this happens you can undertake a small test. Take 15 g of sugar in one go and see whether you experience an immediate improvement. This test will show whether the condition is related to decreased ATP production which is known to cause panic attacks in some people (false hypoglycemia). If you see an improvement from sugar then it means it is related (you can take a look at my other posts to see how to manage that).
Other tests that may be helpful for you: HOMA-IR, A1c, Low-Density Lipoprotein (LDL), High-Density Lipoprotein (HDL), Cholesterol, Triglycerides, Gamma-glutamyl Transferase (GGT).