Your professor might provide a list of topics to choose from... but you might also encounter the freedom of "anything that interests you"! How do you find a topic when anything (that relates to the class, at least) is on the table?
Begin thinking about the type of research you would like to do by asking yourself the questions below. Remember, even seemingly silly ideas can lead you to relevant new topic areas and research questions.
These resources have topic collections that you can browse and explore. What catches your attention?
Take a moment to organize your thoughts. Your ideas may evolve as you start doing some research -- that's a normal part of the process! That makes it all the more important to keep track of where you're going (and what parts of the topic you don't care about).
These are useful tools for laying out your ideas so you can see what the big picture is. Start by doing some free association with your central idea in mind...what do you think of? Go for related themes, expanding the details, or jotting down specific examples you recall. Write down everything. This is the "throw it at the wall and see what sticks" phase. This will help you narrow your topic down.
Starting doing your background research to discover new concepts, phrases, ideas, and keywords to make note of.
If you're not into scrawling lines and bubbles all over your page, you can work within a more linear outline. (If you DO like the lines and shapes of a mind map, you can still outline, too! It builds the structure of your paper.) This is most useful after you've already figured out your topic and what you need to say about it.
You'll put things in an order that makes sense (and you can always rearrange as needed), but you can also note the specific pieces of evidence you have for each point. Even better, start noting which sources are giving you those pieces of info! It'll make writing the paper itself so much easier. This will give you an overview so you can see where maybe you need to do some more research, or add an explanation of something.
Searching for an overly broad topic will get you too many results, and you'll be stretched thin trying to talk about everything in the page limit of your paper. You're not trying to discuss everything to do with all kinds of stress -- focus on a specific kind and a specific relationship.
A manageable topic is narrowed down just enough to be interesting. You'll get results, but not thousands or millions -- and because you have a clearer idea of what you're looking for, you have options for make those search results even better.
If you're too narrow in your focus, you won't be able to find any results.