While I had events before which could have been mini burnouts, but the first one came for me in 2007 when I was around 35 and I have had several since then which got worse and worse each time I had one. 2007 was the last time I worked full time and 2019 was the last time I worked as I found the last one effected me seriously, but each time I hit one, I had to quit whatever job I had at the time as I did not know what was happening to me and I could not describe it to doctors so I did not tell them. I lost a lot. My house, classic car, camper... They really effected me because the year or two I needed off work to recover meant I had no income and did not know what was happening so I could not go off on sick or describe to doctors what it was.
Before the 2007 one, I did experience one or two but they were mild and just needed a but of a rest from the strains of life so recovery was quick. 2007 one I quit a very good job (My answer was to quit ad try a different line of work when I was ready as this would make me avoid what I thought caused me to burn out).