You chose the right guy to come and see your post! My dad and I talk to ourselves all the time and my mom and brother used to think we were crazy. The “head talk” is often just the non-verbal way of kind of hiding the self-talk to avoid embarrassment. It is more common than you might think.
For example, do you talk to yourself when you’re pooping/peeing/brushing your teeth/taking a shower/walking alone by yourself/when playing video games, etc.? Those are times I often self-talk. It might even be as subtle as a whisper, or even no noise at all. How about when you exercise (if you do) and any other times you may be alone?
You’re NOT CRAZY and it is just the impulsive side of your brain trying to keep you amused when you have less stimulation to keep your brain up to speed.
It is very similar to why people are hyperactive when they feel more tired or less mentally “aroused” because the electrical speed of the brain waves slow down and the natural tendency is to want to bring those “back to normal,” or whatever normal is for us ADHD folks.
ADHD brains tend to run slower in neuronal conduction speed, so it is beneficial to keep your brain stimulated even during times of great boredom or while doing activities that are not interesting/exciting. Talking to people is even a way to get some stimulation going because you get a response from others, (or maybe not), but still hearing yourself talk is like talking to someone which is stimulating and thus part of ADHD 🙂