I experienced the same thing when I was taking adrenal drops. When I started taking them I felt more fatigued for a couple of days, then I'd feel much more energetic. When I ran out of drops then resumed taking them the same thing happened.
My ND told me that this is normal in people with severe AF. She said that when one starts taking supplements that work the adrenal s are finally able to rest. After they've rested for a while they function better, and one then has more energy. I hope this helps.