I have significant sleep inertia when I wake up, and after my 10am nap. (It might be what others call 'mental fog' but I've always thought of it as sleep inertia). I try to keep pretty still until around 3-4pm, or else I get very tired and achy. At 4-5pm, I can walk my dog slowly for 20 minutes and feel ok afterwards. After 8pm I can exercise vigorously without consequence. I go to sleep around midnight and sleep soundly. Is this a pattern that resonates with anyone?