I have a similar problem. Intrusive thoughts come to mind and I find myself (mostly mumbling) stuff related to them. I become especially "vocal", so to speak, when I'm alone taking my morning shower, shaving, etc. When we're together and I do it, my spouse will sometimes say: "what?" thinking I was talking to her. I typically just say: "Nothing" or, if she asks if I'm okay (which she sometimes does) I'll say: "I'm just tired". I don't know why I do this. Nor am I aware of any names for it. It's just something that happens. I look at it as simply being a sort of release valve for all of the pent-up depression and anxiety I carry around inside 24/7/365.