For people who have experienced spooky stuff while in bed at night, be it seeing ghostly/demonic figures that disappear in a flash, or sensations of being weighed down, such experiences could be traumatic and cause lifelong fear of paranormal beings.
The good news — such experiences are actually dream-like phenomenon that occur in the process of waking up, or during Sleep Paralysis.
a) Dreaming about your bedroom from the perspective of yourself lying in bed.
b) Being in bed in a semi-conscious state, transitioning from being asleep, to being awake.
Practically, it is impossible to determine whether one is experiencing a) or b).
It is also possible to be experiencing both a) and b) simultaneously!