ex) Childhood poverty, immigration, incarceration, disability, etc.
Once you have a general idea, you can search an article database to see what kinds of topics are being discussed that relate to your general idea. Take a look at the search tips page for databases you can try. As you notice a focus area that catches your interest, you can add those words to your search to dig into that topic further. Remember, it's ok if your research question changes as you learn more, that is how research is supposed to work!