You don't perhaps have a nutrient deficiency? In my case it was an iron deficiency that crept up on me and made me lethargic for months before I got checked out

You don't perhaps have a nutrient deficiency? In my case it was an iron deficiency that crept up on me and made me lethargic for months before I got checked out by a GP. I think depending on your diet, low iron, protein, salt and/or B vitamins intake can exacerbate the lethargic/burnout/lack-of-motivation funk you're in. Also just being constantly dehydrated ain't great. Of course being unhappy at work is a massive deal and will impact all other parts of your life as well - but others have made suggestions around finding a new job. I just wanted to make mention of the nutrients stuff as a CTRL + F brought nothing up.