Quote Originally Posted by Throbert McGee View Post
I would assume that in Russian, a construction with собираться is impossible in all these cases -- in the first two sentences, because there's no conscious agent as the subject; in the third one because vomiting is usually not a matter of free will.
That's right. But I like to elaborate on that. It is not exactly impossible in all these cases, but unusual and adds new senses. The good formulation was cited by Боб Уайтман : собираться= "to mobilize one's inner resources prior to doing something". "Я собираюсь заболеть" is quite common though colloquial phrase nowadays. It means actually that I consciously plan a period of sickness in my life. "Дамба собирается рухнуть" is also possible but has a metaphorical sense, like if the dam is something animate and conscious.

If there is no infinitive after "собираться", it has other but related meanings: a) to get together b)to get one's things together.