Hi retro_chic

the gaps/discontinuity sounds to me like some form of dissociation. Many trauma survivors tend do dissociate, when things get too overwhelming. I'm not talking about DID, more like some "milder" expression. If you think of dissociation as some kind of continuous spectrum, there's mild every day type of dissociation on one end, things that almost everybody tends to do like daydreaming. and on the far end there would be DID.

This "checking out" in order to protect oneself would be somewhere in between. Basically it's your brain going into "survival mode" which might have been important in terms of self-protection at some earlier point in your life. Trouble is, that the brain keeps doing this whenever it decides there's some imminent (real or percieved) danger...
It's got a lot to do with the fight/flight/freeze response, and this form of dissociating would be some form of freezing...

It happens to me a lot, especially when we talk about emotionally difficult things in therapy. I tend to ask my T in the next session to summarize the most important points, quite often by talking about the same stuff, but in a more "indirect" way a lot more really interesting aspects tend to come up. My T often asks me, at what point I checked out... Which again might be really interesting: Did I feel threatened? By my T herself? Or something she said? Or did I feel cornered? etc..
I still talk, and I can still have a fairly coherent conversation, so from an outside perspective it is hard to notice that I'm going blank...

Hope this helps, if not, just ignore...

Best wishes, c_r