If you're not interested in learning more about the subject, or at least answering the question you pose, you'll be less compelled to see it through.
A concept map or mind map can help you think through an idea and allows your mind to identify areas of interest.
The best way to do one is with pencil and paper! Here are some digital alternatives if you like working that way instead.
Make sure your question is open-ended (not answered by yes or no). Consider the following ways to structure your question or topic:
Do a quick search in PubMed or the Library catalog on the subject to see what's been written and if there's something you can build on.
It's important to recognize that your topic is not set in stone and may change as you read more about it.