That is probably dissociation, specifically "
depersonalization/derealization."
You can click the link above and read a PsychCentral article on this topic. During the "surfacing of trauma" time when I had frequent, intrusive flashbacks, this happened almost daily.
It becomes helpful to determine in therapy if this is part of a flashback, as in you did this in the past during trauma and so you are flashing back to that state, or if you are doing it now in response to triggers/flashbacks or retraumatization.
Mine was more the former, and some the later when I hadn't known how to manage my flashbacks.
Since it sounds like you might be experiencing flashbacks without realizing it is happening, I will also link you to Pete Walker's "
13 Steps for Managing Flashbacks" of which you can select among those steps you find most easy and simple to use for you. You can click the link here and print the PDF. It can be most helpful to highlight the top 3 you use, and go over with a roommate or supporter who might be with you most often.
I find that having that person get me cold water to sip and encourage me to drink it when I'm having trouble breathing or can't stop gasping, that it helps cut through the dissociation and gets me out of Flashback fast. If I am alone, I go get my own ice water in a daze. It takes a lot of determination and really is not fun, but once I get moving and get the cold water in me, I am usually able to recover more quickly. I learned that cold works against the body's dissociative response from my last T. I also open the window if driving or turn on the A/C. Maybe you can try something cold, like a cold gel pack from the freezer or a cold beverage, when you start to feel this way and track how many minutes it takes to pass out of this feeling.
I wish you well. Don't be too alarmed; it's just dissociation and that alone cannot harm you. You can learn to control it.