That is sleep paralysis. I've been independently studying all sorts of subjects surrounding my own experiences with sleep paralysis for over 20 years. Only in the past 10 years have I been able to get actual medical information.
To explain this as easy as possible...
Sleep paralysis is a normal cycle during rem sleep. Triggers in your brain shut off skeletal muscle activity as we go into rem sleep. Literally paralyzing the body without paralyzing organs. When we are out of rem sleep and move toward consciousness, triggers in the brain turn the muscles back on.
Sometimes, these triggers are either delayed and you wake up paralyzed or they are premature and paralysis occurs prior to going into rem sleep.
What i've been highly interested in are dreams, visions and any other senses experienced while stuck between wake and sleep. I'm also interested in medical history of sleep, psychological and metabolic conditions or disease in the family of those who experience sleep paralysis.
I'm finally in college to try and make biological sense out of it...Including the visions.
Are the visions clear? Can you breathe when paralyzed? Are people in your family common to diabetes, thyroid complications, mental health issues or sleep disorders like narcolepsy?
Btw...Sleepwalkers are the opposite. The triggers neglect to shut the skeletal muscles off in rem sleep or prematurely switch the muscles back on before going out of rem sleep and so they act out what they are seeing behind their closed eyes. They are in rem sleep. When we experience sleep paralysis while conscious, what we are seeing is happening out of rem sleep.
Eyeon