Abby, We are mammals. Mammals are supposed to nap.
Perhaps your cortisol levels are tanking earlier every day. They are at their highest in the morning - which is why they should be tested at that time - and decrease throughout the day. Maybe it's time to see your endo to have a thorough look at everything.
In science, there are a lot of axioms they refer to, such as Occam's Razor or parsimony. Basically, "Keep it simple, stupid." Often the most simple explanation is the right or best one. Of course, they probably weren't referring to MG.
Annie