Whenever you feel daunted to the mere possibility of the daunting task to write, well, the first word can make the cut. Keep writing and absorb yourself into the moment of writing, specially if you are in front of a possible PhD Thesis Dissertation.
However, this task, you can break it down in parts. Small bits, small chunks so you don’t have to digest a big amount of words in one sitting.
Go bit, by bit, if you want, but at least give yourself one hour a day until you have a good amount of words, and maybe, just maybe a possible great idea or two.
But how you ignite your writing, specially if is for a dissertation. Well I guess the first you have to do is to remember what is the problem or the question that is driving the research you are doing. So yes, go ahead and figure out what is that big question you want to answer.
Each time you are confronting that white page, seek to ask that big question, that big problem and find a possible answer, find those words that might be in your head but are not pouring to your fingers. Do it loosely don’t be afraid.