how to look for a research idea?

hi guys, so I have worked on multiple research projects that are cross sectional in nature. getting a research idea wasn't difficult because all I had to do is look for studies about knowledge and awareness of a certain thing that hasn't been done in my country and here we go. there is a research idea,.

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but now, I would like to try doing another methods, such as cohort or anything else.

how can I get an idea for a cohort study?

I'd like to conduct a research in otorhinolaryngology, would it be impossible for a student to conduct a cohort study? thanks