Well, mine comes and goes, so of course it's normal! :geek::rolleyes::alien::bag::cool:
I guess "normal" for everyone is a little different; I read a bit about people who formerly did not dissociate or have derealization, have an adult trauma, and then do. They find it very different from their former "self", what they felt was their "normal" state, and have a lot of trouble adjusting.
However for those of us who started doing this stuff as kids (and then maybe part of our brains decided to dissociate the memory of starting to do it), we might "function" -- often quite "well" . The "structural dissociation" model has been really helpful to me in having a framework to better explain some strange differences and experiences plus the problems... also for many years I could not progress like friends who had childhood trauma but maybe weren't so dissociated from their trauma feelings; I don't think that therapists around 1990 really understood that stuff (many don't now!)
I am not certain what part of the brain makes the dissociation "come and go", but it's definitely not the part sitting here thinking what words to use... It can be safety-related for me, I think, so maybe reptile brain? I shouldn't even guess because I know nothing about the brain that's not in Wikipedia; apparently we share lots of the brain with reptiles.
I just heard a thing on how a woman made snakes in a zoo (seem to) feel safer by sitting quietly with them, day after day... These snakes had been impossible to handle without special head holders. She just sat quietly with them... An anaconda finally came and curled around her leg, not hostilely. Now the other people like veterinarians can handle these anacondas with no trouble, the snakes are reproducing too, which is rare apparently.