I have this problem on a smaller scale. Here are some things that work for me:

Set a very small goal that can break loose the procrastination. For example, when I could not get started, I made a goal to write 3 sentences a day for a week. (They did not even have to be good sentences : ))

Ask someone to type what you say or use a dictation function (I think Word has one now). It can be easier to break the cycle if you just explain what you want to say to a person as they type.

Make an outline of 5 main topics that you want to talk about. Write 1-2 sentences under each heading.

Ask for editing help and send small batches to this person. For example, ask a friend to check your grammar on small one page writing sections.