Hey Bill, when I've had something relatively short to write, but I've had trouble getting started (say, a short essay for a college class -- I wrote twenty million of those), I made a deal with myself that I was just going to write a certain amount (say, 200 words) with the intention that I wouldn't use any of it. It would be "throwaway" text, written on my subject but not to be included.
Often I'd use these words to write preamble or background type stuff, which would end up getting me rolling right into what I was trying to write.
Other times, I'd make this deal with myself and start writing, only to find that what I was writing actually was the essay itself, and I'd agree to break my agreement with myself, and just go ahead and use it.
Whatever the case, it seems like that agreement with myself that I'd start writing words not intended to be used for the project/essay/review/whatever, would break the blockage and get things flowing.