The human brain is an amazing and mysterious thing. With all our technological and scientific advancements we've still just scratched the surface. It seems as if you could have experienced sleep paralysis, another thing our brains do that science doesn't yet fully understand. It could be that you did indeed experience something supernatural. Keep a record of unexplained occurrences, that might be helpful if you need to bring in an investigating team in the future. If it is sleep paralysis, this might be useful...
How can you prevent sleep paralysis? According to clinical research, you may be able to minimize the episodes by following good sleep hygiene:
get enough sleep
reduce stress
exercise regularly (but not too close to bedtime)
keep a regular sleep schedule.
Taken from this page...