What are some signs that a person is suffering from a burnout?

I am starting to wonder if I am burnt out. I never feel rested, even if I sleep 8 hours a day. Whenever I plan something, I feel it to be a monumental task, for example, I try to train 4 days a week, and just going to the gym feels rough.
I have noticed that I have lapses in my memory and I am having a hard time remembering things. I do not find joy in many things anymore, and I am often more focused on doing things "right" than having fun.