I have this issue that occurs seemingly at random. I suffered from no known mental or sleep related issues. This issue comes and goes seemingly at random. The only thing I can trace it to is when I am having trouble sleeping. I have my eyes closed when this happens, and I am preparing to sleep. However, my mind will still be active, and I will not be close to sleep.
What happens is I see shapes. A square, triangle, and circle. Just those three. Sometimes I see all three, sometimes just two, but I always see at least two.
They are always inside each other, the biggest is on the outside, smaller on the inside, but all the shapes can be the biggest or smallest.
For example, the square could be the biggest, with a smaller but still large triangle inside. Then there is always one incredibly small shape in the middle. Just barely big enough to make out its shape.