If you’re struggling with finding a proper topic, ask another person to suggest a few + write a raw outline. It is not free, but it really is a good idea. The customwritings.com review that wasrecently written by writingpapersucks is a good guide for finding a helper.
When you set out to write your doctoral thesis, you can expect a lot of research even before you start. In the beginning, you will need to read scientific literature to find your topic, and later you will need suitable sources to support your research and justify connections. It is important that you do not waste any time. Get an overview of relevant sources by reading abstracts rather than complete essays or books, and only work through important chapters.
Remember topics that fascinated you during your studies and research the current state of research. Your former instructors can also give you tips. Consider whether your research can add to the body of scholarship in your field and, in parallel, see if there is already a doctoral dissertation on the topic. If you feel that you can contribute current findings, you should be clear about the extent to which your work will provide new insights and trends. Basically, you proceed in a similar way as when finding a topic for your master's or diploma thesis, with the difference that you delve deeper into the subject matter for your dissertation.
What you develop in-depth at the beginning of your research for the dissertation may be helpful by the time you defend your doctorate. You may also be able to deepen your master's thesis or expand on individual aspects of it.