I believe that self-motivation is a great start to start and conduct research work, but much like what Dennis has mentioned, I also believe that a researcher's mind should be sharp and curious. As a young researcher myself, I would like to believe that self-motivation itself is sufficient, but there's so much more to research than that. You need patience, resilience, and most importantly, the ability to get back up when faced with failures.
With the right mindset, experience, and training, a researcher can come up with the most critical and relevant research questions and this is where most excellent researches sprout from. It is also important to remind yourself why you are doing what you are doing, because ultimately, research is partly done for personal gain but also for a naively bigger picture, that is the advancement of the scientific community.