When I go to bed I'm not really tired, but when I first wake up, I'm EXHAUSTED!?

I know this happens to most everyone,
but why does this happen?
yea it happens to me - sometimes.
i was told to change my mattress. i think you should stop sleeping so late (in
the nights). this might sound like ur parents sending u to bed at nine every
night, but if u went to bed every night for 2 -3 weeks (maybe not even that
long, it depends on the individual) and woke up at a same time every morning,
where u have had 8 hrs rest. then u should be fine.

if that doesnt work, try to above, with a 'proper' mattress.
might be many things 4 for different people. my doc once suggested i might have
be depression or some kind of sleep disorder. but as i said, it could be many
things. probably normal
didnt mention ur age but i had sleep apnia now i sleep fine and wake up
fantastic(wear sleep mask)