This happens to me when something upsets me and I become 'mute'. I want to vocalize, but can't. I can just make sounds and grunts, sometimes even those are impossible. I communicate in writing. However, something strange started happening - I started having these episodes after waking up. I had one a few months ago after waking up from a nap (had a bad dream) and one this morning (don't remember if I had a bad dream). I woke up and wanted to speak, but I couldn't coordinate all the muscles needed for speech production, so I just grunted the words. No one could understand me, even though I did. I just had to wait until my brain 'woke up'.
I had a theory that it must have something to do with the motor cortex controlling vocalization muscles, like the laryngeal motor cortex (LMC). According to this article, patients with lesions in the LMC
Quote:
[...] are occasionally able to initiate phonation, such as grunts, wails and laughs, but do not succeed in voluntary modulations of pitch, intensity and the harmonious quality of their vocalizations.
I don't think I have any damage in the LMC, but it might be that whatever overwhelms me triggers some chain reaction and I can't speak. They don't know all that much about LMC yet. This is only a hypothesis I have since it's been happening to me and I want to figure out what's going on. Bad dreams overwhelm me.
When I go 'mute' while I'm awake, it can take a long time to recover. It usually happens when I watch something on TV and I get shocked by a scene, or when someone says something provoking. I find myself talking without realizing it, and then I yell "I talked!" because it surprises me.
Maybe this qualifies as temporary verbal apraxia.