A good problem statement or research question is manageable in scope - not too broad, but not too narrow. It is often helpful to start with a broad idea, then narrow your focus by brainstorming related ideas. If you have a general area of interest, you can think about various issues in that general subject area. Your research question should be clear, focused, and complex enough to allow for adequate research and analysis.
You'll find information to help you develop a problem statement or research question for your paper at the links below.