So you have decided to go for your doctorate degree?
Doctorate degrees require a dissertation and dissertations are based upon a research topic. The time to select a research topic is during the course work and not at the end of course work. When beginning your course work, as questions come to your mind log them. Building a list of questions will save time when it comes to the part where the problem statement is required. Focus on having more questions than just focusing on one the reason is due to the fact that you want to look for limitations in the study to find a topic that can be approved.