I don't know when it started, but I've been doing it for several years and whenever I've tried to stop i feel a huge mental strain so I just let myself whisper, mouth it out, talk whatever I feel like doing. I do it so often it's embarrassing. People walk up behind me and catch me in full on rambly conversations I am having with myself..I am socially isolated and don't have many deep relationships so I think that's my trigger. It's like verbalizing my inner thoughts. I have to do it. I don't know why. I just gotta verbalize it. My brother also does it but he yells his thoughts out in the form of conversation and it's weird as fuck but equally comforting to me somehow. It happens. We exist lol