Yes-lots; definitely!

Sometimes I feel like a child personality takes over, not realizing until I'm a bit into it. I agree with kecanoe that it is DID, and that it is common than generally recognized. I think a big element of trauma, PTSD, DID etc is memory storage/processing/retrieval.

Other times it happens when I am letting myself be really vulnerable, like talking to my therapist about strong needs I am experiencing. I think that's common too. Still other times it just happens when I am freezing, feeling dizzy, another type of dissociation.

Sometimes my voice goes down to such a soft whisper, just like you described.

There seems to be various facets of this involving energy/arousal, personality, and defense. Not that they are discreet concepts, but I just wanted to point out there can be different things causing this.