I have had the same feeling too during a power nap. It feels like a reboot to me. Perceptually when I wake up I panic thinking it must have been hours then I look at the watch and only 10 minutes have passed.
Yes, that. I can wake up at 8, accidentally fall asleep, and feel like hours or days have passed and panic, but it's just 8:15. Dreams are so mysterious it's weird, in our age of science.