Why is it that i move around and do stuff im not that tired but when i sit back down to do other work why do i feel tired and i felt tired everyday? what do i do? is it mostly due to me sleeping late and not getting enough sleep?

Basics: Feeling tired or drifting into a nap when sitting/watching video/reading is often linked to poor or inadequate restorative sleep. Sleep needs are based on age, physical & mental exertion, growth or recovery from illness. At 17 the estimated need would run 7.5 to 8 hrs or more. The body tends to keep you alert during physical movement as a protective device.