Yes. This is very much what I experience myself. Thinking about it, it also makes sense that the emotional reaction to a situation, that triggers a reaction also from a past experience (basically layered over each other) sounds like an invitation to check out. Thinking about it in that way makes total sense. It's too much to take in and process. It does feel like another part of me steps in when that happens. There is that feeling that I'm there, but I'm not. I'm talking, but it's as if someone else is doing the talking and I'm listening, from the inside. Sometimes it's kind of dreamy feeling.
At the point I am right now, I'm having a difficult time catching it before it happens, to offer compassion.

I'm working on journaling what I feel/hear from other parts of me. My journaling is geared toward understanding the feelings and purpose of the other parts of me that I have found, or that have found me. I listen and write what my heart hears.

My thoughts are, that if I can understand their feelings and purpose we can work together. If I value them and do show them compassion and gratitude for why they "are" that validates them. I want them to be validated and honored for what they have done.

As I'm learning what a real and honest relationship, with boundaries, is - maybe my other parts will trust me more to hold the boundaries and feel it's safe. Maybe they will trust me enough, to not feel that one has to step in, take over and I go numb.