The first time i experienced sleep paralysis was a couple years ago. The doctor suggests it happens to most people at least once in their life. It's due to the regular phases of sleep falling out of order. When you go to sleep, your mind sleeps first, then your body until you are in deep sleep, each process of sleep lasts approx 3-4 hrs before your body wakes up and then your mind. Older people can often manage on just one phase of sleep, whereas teenagers can quite happily sleep for three phases.
With me, i would wake up with sleep paralysis shortly after my body sleeps, when i should be in deep sleep, but for some reason my mind wakes up out of sync, and the following is what i experienced:
The first time, i felt like somebody was dragging me out of bed and then lifting me up, i was floating towards my bedroom window 9 floors up, i thought a ghost was trying to kill me.
The second time, i was laying on my stomach and felt i was being held down, the more i tried to struggle, the harder the pressure forcing me down became.
The third time, again on my stomach, the same feeling of being pushed down, i managed to speak out, and said " go to hell you evil witch", before the pressure dissipated and i heard a thud as if a demon was angrily banging at the wall.
I've had sleep paralysis on a total of five occassions, i didn't know what it was until after the first three, so they were scary, the last two however, lasted much shorter because i knew what was happening to me and so didn't panic. You just have to wait for your body to catch up and wake up.
I'm not sure if it is a scandinavian country or an african one, but there is a saying that 'the devil has got your back', a reference to sleep paralysis, on account that those who first experience it without knowing what it is can feel like a supernatural force is in the room with you, holding you, attacking you. When in actual fact it is your mind tricking you into believing that because you are awake and unable to move, that something or someone must be preventing you from doing so.