From these comments, it seems actually not that uncommon. Yet given the vagueness of the symptoms / inability to diagnose accurately, it doesn't really have a name and is not considered seriously by the medical profession.
I exercise (primarily weights and yoga, plus cardio here and there) 3-4 times per week, eat incredibly healthy (lots of greens and lean proteins), get enough sleep (7-9 hours). My blood pressure, weight, and BMI are great. I have sleep apnea and am allergic to wheat but have treated those as best I can (the former is difficult, the latter is quite simple).
And yet, I feel sort of "removed." Constantly fatigued. Kind of like being in caffeine withdrawal (and no, that's not it). Don't feel as strong as my exercise and age (late 20's) would have you think. Always dehydrated. Very little "vitality."
Around the same time period, I was "floxxed" by Cipro, and got Mono. My best explanation is that it has something to do with one or both, but no doctor has ever figured it out. By all accounts, I'm very healthy. I just constantly feel like shit.
"unrefreshing sleep, always feeling under-oxygenated/undernourished even when having a very healthy diet, a constant sense feeling "tired and wired", or "spinning the wheels"; i.e., at-once feeling exhausted, but also like your body/mind is working at full speed, but not being able to get much forward momentum in life."
Completely, utterly on point. Thank you!