Hello rhapsody,
something I am finding more and more is that many people experience things that seem quite different to me at first but when I look closer there are real patterns.. so for example I can control what I write (unless I open up and allow a stream of consciousness to come out) but then I have a highly controlling part that deals with the majority of day to day life and that involves a lot of writing.
What I can't "control" is things that are
drawn because somehow that seems to access a more primal/younger part of my brain and then I experience what you have talked about. So I can start doodling one thing and end up in a whole other place and I don't know/remember how I got there.
I think its because more repressed parts see in pictures and images rather than words.
It sort of sounds similar to what you are describing.
Sorry if this is nonsense.