For me, it's definitely the internal monologue. Worse is that I have a form of OCD (repetitive thoughts) so this monologue gets stuck in a 'loop' and I end up just repeating the same sentence, or part of sentences to myself. Drives me nuts.
Makes me wonder if people without this 'internal monologue' experience this kind of OCD in the same way..
Similar experience here.
I find that as my internal dialogue begins to loop, my frustration grows with being unable to break the cycle. I have an awful temper (see: anxiety disorder) that seems to stem from this. Often if I've just lost my temper, postmortem introspection/analysis indicates that I was thinking the same <5 thoughts in a row in quick, vicious succession until something "short circuited" and I quit thinking altogether - just angrily reacted.
I'm OCD but I definitely don't internal monologue. I do get stuck in what I call a "simulation loop" as I play out possible scenarios in my head and I can totally talk in those, but I have to intentionally "pretend to talk to myself" to talk to myself. In general the only time I hear "a voice in my head" is when I imagine/simulate saying something to somebody else.
I wonder if that's the same thing going on inside a brain as getting a song stuck in your head? That happens to me fairly frequently - the voices in my head will be repeating the same line or verse of a song over and over...
Until you've 'said' it just right? I definitely have OCD tendencies, and this sounds like me in my 20s. What helped me was distracting myself with another line of thought.
Makes me wonder if people without this 'internal monologue' experience this kind of OCD in the same way..