I've never experienced important health issues, but since being a kid I noticed that staying still in squad pose and then standing up would cause very bright dots moving in my vision that would slowly go away. These should be caused by blood with low oxygen moving from my legs and into my brain. A few times my vision got very dark and I experienced a headache and eye pain, and felt like passing out.
I've also became temporarily blind due to high voltage exploding wire at a few inches from my face. I remember the perfectly white line of the wire and the colors gradually but quickly becoming average gray from the middle to the sides of my vision, then the wire and the color disapeared with "no signal", there was no recognizable color, not even black.
You are likely describing “photopsia”, which can express in many ways and is sometimes referred to as “seeing stars”. I myself call them “fairies”, as for me they are tiny rainbow scintillating spots that spiral around and disappear between 1-4 seconds.
They are produced when a sudden shift in physical pressure on the retinal cells occurs. Blood pressure shifts are the cause when standing up or sitting down, and is typically a concern. They can also be produced by physical impacts against the eyes or head.
I've also became temporarily blind due to high voltage exploding wire at a few inches from my face. I remember the perfectly white line of the wire and the colors gradually but quickly becoming average gray from the middle to the sides of my vision, then the wire and the color disapeared with "no signal", there was no recognizable color, not even black.