A few comments:
1) Look at the background in Sagittarius in the Milky Way. The sky appears 'grainy', which is incipient resolution of extremely faint multitudes of stars. You might also see this in Cygnus with the naked eye.
2) Look at the ground or surroundings (but not the sky) once you have dark adapted. You may see, as I do, your visual reality break up into a series of dots--the 'pointillism' of visual reality when insufficient light is entering the eye. Is it noise in the retina? Perhaps.
3) Look at a star cluster of moderately bright stars (say, NGC7789 in Cassiopeia). Do you see the stars all surrounded by very slight fuzziness that makes the stars look as if they all sit on stalks pointing at you? If so, this can be evidence of dew beginning to form on the optics (eyepiece, or lens or mirrors). In fact, this can cause the 'mottled sky' effect you mention.
4) Visual noise appears in differing ways. When I look at a galaxy cluster I can 'see' galaxies where there are none, and sometimes not see ones where they really are. When you observe at the limit, visual noise often appears 'real'.
5) Have you sought stars at the very limit of your scope by using some magnitude charts for specific areas? Stars at the very limit are only visible to averted vision a small percentage of the time. If a star winks in, it appears as a very small pinpoint.
If a galaxy or nebula fragment just winks in, it appears as a slightly brighter portion of the background sky. This makes identification difficult. I usually have a chart of the area of the faintest targets so I can look exactly where it is. This increases the odds that something that winks in and out of visibility is real and not just noise in the eye+brain combination.
6) Stars "move" when you stare at them if the patterns are arranged to fool the eyes. A recent thread here on CN had a chart with a series of ovals on it, arranged in vertical and angled rows. The ovals crawled back and forth and seemed to undulate. When you stood back several feet from the monitor, they stopped moving. I often see objects at the limit, especially stars, crawling in position. This is an example of where the eye and brain are being fooled.
if you study many of the references on the web concerning vision, you will see how easily fooled the eye is. Stare some time at a uniformly black piece of construction paper in a poorly-lit (or very dimly-lit) room. The black paper appears mottled and sometimes shows gray patterns on it. This is the poor visual system nature gave us to deal with really low light conditions.
Despite that, we do have better night vision than you might expect for a daytime animal. It probably had significant survival value in the youth of our species.
But it obviously isn't perfect.