I've been sort of burned out a few times for various definitions of same. A couple were just pretty intense phases of projects--both in tech and non-tech--where I just needed a bit of a break afterwards.

The other was I was just ready to check-out late career. Didn't have the interesting earlier career work any longer. I sort of made it work but really didn't care and timeframes were such it didn't make sense to go elsewhere for a bit.