Soliloquy: The act or custom of talking to oneself or talking when alone.
When I was growing up, I would often overhear my grandmother and mother talking out loud to themselves. They'd count up something, make an oral mental note, mutter an exclamation or make a declaration, shoo away a pet, scold a child - and at other times, deal with a frustration by 'talking it out', out loud. That doesn't even count all the singing, humming, Irish 'diddly-dee'ing', or whistling. Some of it I suspect was just to deal with the continual work that never seemed to end, or the solitary nature of the majority of their long days. Whatever the reason, I grew up around hearing them vocalizing their thoughts, and felt it the most normal thing in the world to do.
a method to clarify my thoughts, lay out problems, work through frustrations, or express deeply felt emotions. I don't really think about it, and have even been caught doing it by other people around me, who find it very odd.