You get a full night's sleep, have an average morning, and end up with a 2-3 hour nap in the afternoon. You are most likely:
I said brain, tired, like if you're in a situation all morning of heavy sensory and/or emotional stimulation and your brain just needs to shut down for a bit and reboot.
I don't nap. If I nap it means I WILL NOT sleep. Sleeping is hard enough if I've only been awake 16 hours (i.e., pretty much impossible).
Dying. I never do that...
If either, I must be really mentally exhausted.