The good thing about history is that there is almost an incalculable amount of topics, subjects, etc. to choose from that fit your interests. Now here's the bad part; since there's so much to choose from, it can be challenging to know where to start or what you even want as your topic!
Are you an enthusiast for military history? What about gender studies? The history of medical technology? Women's history in Asia? The political history of South America? An important first step is looking at the broad subjects that interest you. Your personal preference is a big factor when you start research and if you decide later on that it's not a topic you want to pursue, it's easier to change early on rather than later.
Once you pick a subject, you can begin narrowing down to a specific topic. From here, you can begin looking into what sources are readily available and start some preliminary work. It'll help getting your research momentum going if you start thinking about what direction you wish to pursue.
Now that you've got a specific topic in mind, it's time to investigate and learn what you can before you begin writing. If you know the material well, such as extensive reading, gathering sources, and seeing work by other authors, this will further shape what you want to research.
And now it's time to think about that big, daunting, Greek sounding word we feared as middle school students and even as high school freshman...THESIS. Keep in mind, a thesis is not ironclad. This means they can change during the course of your research as you look through more sources that can either improve or challenge your thesis.
The final point here; how people start their research is subjective and inspiration varies from person to person. If you talk to a published researcher or author, they can tell you about their process and if it works for you, give it a shot. If not, you can embark on your own research path and find what'll make you a thorough researcher.