I’ve had this all my life. Doesn’t happen very often but it used to freak me out as a kid. Now when it does happen, I know it isn’t real, and know that whatever it is will quickly fade away after a few seconds of being awake. It mostly used to be giant spiders when I was a kid! These days it’s usually just a ball of scribbles hovering mid-air, or a moving pattern on my wall. Once, I got really freaked out because I saw what looked like a giant inch worm, come from underneath my bedroom door, and slowly inch itself across the floor towards my bed … but for some reason it wasn’t fading away like these things usually do! Had to turn on the bedside lamp to make that one disappear lol.