Hm. Might have solved the question of the odd physiology in the morning when working here. Felt the ventilation come on (a few hours into the occupied hours), and shortly afterwards, the dull muscle aches associated with the difficulties came on. Presumably, after the morning workout, the body is more prone to shutting down when deprived of oxygen, and that's why I had the difficulties with spontaneous sleep and discomfort.
Bit like the church in Cleveland that I used to run to in the AM from the gym. They seemed partial to the dim airlessness usually found in churches, and I almost passed out a few times from it.
Without oxygen, the people perish.