So last night turned out almost exactly like I thought, except that I almost managed to fall asleep pretty early.
I had gone to bed relatively early, I was pretty tired and for a good while it seemed as if I would actually succeed in getting a good nights sleep. But then, just as I was drifting off, my right arm suddenly twitched, and in seconds I was back into a state of wakenness. Just as I was so close to sleeping mere minutes ago, I now felt more awake than I had ever been during the whole day.
What followed was the usual tossing-and-turning, trying to find a 'good spot', not too hot, not too cold, cursing the pillow for being so uncomfortable, etc. Accompanied with this was the usual line of thoughts that go with insomnia: bad memories, recollections of situations and moments I regret/feel ashamed about. Not a pleasant night. In desperation I went up and got another pillow, and at first it seemed to have worked, as I stopped thinking about weird crap. But as it was, the pillow was a really thick one, raising my head a bit too much. So I switched back to the usual pillow. Better the devil you know, right?
At one moment I looked at the clock and saw that I had been lying awake for more than two hours. How long I lay awake after that I can't say.
Oh, as for the title, that's what the involuntary twitches are called: myoclonic jerks.