Welcome to the forum!

The visual and sensory hallucinations you're having sound like Hypnagogic Hallucinations (HH), which are caused by REM Atonia, a normal part of the process of falling asleep - we just don't always notice it because we're usually already asleep by the time it happens. REM Atonia is responsible for shutting down our muscles when we sleep to prevent us from acting out our dreams in real life, so if your mind is still awake when it happens, you'll notice this paralysis as it happens (not to be confused with Sleep Paralysis, which is a medical condition that causes frequent paralysis episodes at night. More info here: http://www.dreamviews.com/dream-yoga...explained.html ).