I can relate to the habit of ruminating when I'm alone. I think it's fairly common to focus on and analyze our past, present or future, but I'm not sure if there's a specific label to attach to such behavior. While it can be beneficial sometimes to do such analyzing, it's often more harmful in the sense you may focus too much on the negative and/or obsess about it because you're not able to find an explanation or a solution for whatever it is that you're focusing on. The other downside to excessive rumination is it can be a distraction that prevents you from enjoying the minor and major things in your day-to-day life.
What I've found helpful to change this behavior is talking to a therapist who understands how I think but is also familiar with techniques to reduce unhealthy and excessive negative thoughts.