In the few times each year when I actually sit at my keyboard with the intention of writing, it's because my head is filled with indecipherable noise and more often than not, it happens on the cusp of my sleep and waking hours.
The only way that I can describe it, is that it's like being in a seat in a movie theater with a different movie being played on each of the four walls. A random hodgepodge of babble and dialog, chatter and conversation, all going on inside my head from no discernible outside stimulus.
I will usually get up and jot words across the screen, more like a random page tapped from an unwritten diary from some point in my youth...at times fifty words, at others, five hundred.
Sounds like an interesting experience I think :)