Oh yes, I get like this a lot. It can last an hour or weeks at a time. I haven't been able to link it to anything (being sick, bad weather, "time of month ", etc.) it just seams to come and go as it wishes. I have tried all kinds of ways to "snap out of it", caffeine, walks, naps, etc and nothing seams to work.
It is different than just being fatigued. It's more like walking around in a dream I guess.