One of the classic procrastination patterns is the "I haven't gotten my research done" ploy.
It's a trap; it's deceptive, comforting, perhaps--"If I just read this book and those articles, then I'll be ready to write; If I can just organize my research materials, then I'll be ready"--ah, that bright and shining future, where you know enough to start writing!
It's a trap. It's a painful, unproductive pattern.
The hard part about writing--which is also the valuable part about writing--is the part that's not like reading. The hard part about writing is in making something that works. It is in organizing your thought. The hard part about reading is in trying to observe what is there. It's completely different.
Writing is like speaking: it comes from inside your head.
And that means that you have to expend energy to organize your thoughts. And to find words to represent those thoughts to share with another person. We struggle with this all the time; there are a whole slew of stock phrases that relate to this precise struggle--"I'm speechless; I couldn't find the words; there aren't words to describe..." and so on. The battle with writing is to find your own words. It won't happen while you're looking at other people's writing.
In the dead of night, you're woken by strangers who pull a hood over your head, bind you hand and foot, and take you away.
When they take the hood off your head and the bindings off your wrists, you're seated at a desk with a pen and a pad of paper.
"Describe your dissertation project in 350 words (give or take 50), or you'll never see your family again," they say.
What do you do? It's obvious what you do, and realistically it takes you a couple of hours at most because it just doesn't take that long to write if you focus on it.
The knowledge is already inside your head. You studied for years to get to the point where you're being permitted to propose a dissertation. Use that knowledge. Trust yourself. Put away the freakin' books an articles and trust that you learned something from all that reading you've been doing.
You're home for Thanksgiving and a subject related to your topic comes up. Maybe you're writing about something--anything really: history, physics, engineering, designing musical instruments, raising pets, making crepes; it doesn't really matter what--and something related comes up in conversation. Don't you know relatively a lot about your subject? At least compared to the non-specialist?
You've got to write. Writing is like teaching: it forces you to learn again and in greater depth, the subject you have been studying. When you read, and when you learn, you can rely on intuition and ideas for which you have found no expression yet. When you write, you have to struggle to make explicit the intuitions that have previously guided you.
If you do some writing, that doesn't preclude doing more reading later. But if you say "I can't write until I'm done reading," then writing is precluded until you're "done."