Burnout doesn’t really come from too much work, you can be swamped to the brim and feel no burnout. Or you can be sitting bored for 8 hours at your desk stretching out 1 hour of responsibilities to last all day and feel super burned out.

The real cause of burnout is toil for no reward. It sounds like whatever used to motivate you to get shit done isn’t there anymore. Any amount of work you don’t believe is worth the effort will make you feel burned out.

A good book about this is Peak Performance. Pairs great with The Passion Paradox. They cite more researchy/academic sources, if that’s what you’re into.

I’d suggest starting there. Looking into what used to motivate you, why it’s missing, and thinking deep about what it is that you do want to do. Then find ways to do that.