This is a pretty wide question.
I will start by onboarding data that contains information to your liking: Planned reboots, Unexpected Shutdown, and Shutdown.
Different OS (and tools) report differently on these kind of events.
when you have the relevant data, create query/s that answer your questions and save them as report / alert / dashboards
I believe you meant unPlanned reboots, right? We are also looking for a way to get the same report. Were you able to implement this?