I'm sorry if this comes off as a bit condescending, but burnout has a precise medical term, and the term itself is widely overused in other contexts which dilutes the meaning.
Burnout could be characterised as prolonged exposure to stress in work-related environments. It usually takes years, months in therapy, it very often causes career change. Many people never get out of it, especially not without support.
Everyone has periods when they feel a bit off, or a bit under the weather. What you describe is definitely not burnout in the medical sense of term.