Part of the supervisor's job is to help the student formulate this question. Some people can go off on their own for ages, you don't hear from them, and then they appear with a big chunk of work. Others get lost and frustrated in empirical material. If that happens, Brawley takes them back to their original question. Getting sidetracked may not be terribly unusual.
Students start with lots of energy.
Then, midway through the process, it wanes. It's important to fire them up again somehow, so they can finish. Everyone agrees that the process is daunting. Unfortunately, there is always more involved than simply sitting down to write a lot of coherent, intelligent pages. Everyone needs money for food and rent, and some need it simply to carry out research critical to their dissertation.