I have frequent occurences where I will nap during the afternoon, fall into a deep sleep, and I can see the outline of my ceiling and wall, but my eyes are closed, as if staring at a picture for a minute then looking at a white wall, the picture burning into your retina, you know, leaving the outline? That type of thing, but it feels like it lasts for a few minutes.
I try to open my eyes and they feel like they are glued shut. This usually ends with me forcing myself to shake my head to wake myself out of the trance, and I usually awaken feeling pretty exhausted.
Sounds odd, I know but this has happened plenty throughout my lifetime.