It happens to me too, if I sleep for less than 3 hours I feel even worse when I wake up but if I sleep for 8+ hours I feel great. The amount of times I've tried to take an hour nap before rapidly finishing coursework on deadline date and ended up wanting to just die.
Depends on how long you sleep. My hour and a half naps never leave me tired afterwards.
This
Your body goes through an entire sleep cycle about every 1.5 hours. If you wake up between these cycles you tend to feel more tired. You can look into sleep cycles on line there's tons of info on it. But that why when you nap for 30mins-1hour you still tired usually
