I've been dealing with this topic myself for about 3 years now.
Some signs you're starting to burnout:
It takes longer than normal to get started on a task at work (or personal project).
If it feels like progress is comparable to pushing a huge boulder up a huge mountain, daily.
You stop caring about it. Could be work or a hobby. You have no interest in a decision to be made or the final result.
I wrote more on the topic here: https://medium.com/@patrickbjohnson/what-is-burnout-e1eaa32a291
Use apps like Headspace or Calm to get started
Say "No" to 90% of things.
Write down your work, and life, priorities. Refer to this daily or weekly to ensure what you're doing is aligned with those priorities.
Talk to people.