Amazon affiliate site( authority site )

Hello everyone I am back again with some newbie stuffs to ask again and need your help
I am currently working and studying for Amazon affiliate site tbh I am preparing to build authority site and targeting to monetize by Amazon affiliate
I am now stuck on niche ideas
Everyone says focus on something you love and tbh I really can’t figure out on which niche should I go ( I am into body weight stuff I mean I love doing body weight exercises and can’t go for it as fitness is highly competitive )
Can you guys help me how can I look for niche ideas? ( i am planning and know a little bit to filter if the niche is profitable for long term and easy to rank still need to look and research about it more tho )
Any help please on how can I find niche ideas?

Brainstorm lots of ideas and then use keyword research to look for high volume keywords.

If you love fitness issues, you can choose a sub-niche. And if you are good at developing content in that area, you will slowly gain authority and even outrank the major fitness niche sites. Just try niching down further to a specific component of fitness.