Seeing is the term in astronomy for how the view of the sky looks through your telescope. It can vary from night to night, even on the same site, due to atmospheric conditions, like turbulence and temperature differences. Sometimes this can make a difference between sharp, steady views of the Moon and shaky, shuddering images of stars. The best way to avoid poor seeing is to find a dark, open spot away from cities, buildings, and trees where the atmosphere cools more rapidly at night.
Another factor is the surface you’re observing from, such as grass or asphalt. If you’re parked on a hard, hot concrete pad it will radiate heat for hours after sunset and cause bad ground seeing. It’s best to use a pad of firm grass which will absorb the heat and cooling effects of the night air and help with your seeing.
You may also have a refractive error such as short-sightedness, long-sightedness or astigmatism which can cause blurry vision. If this is a constant problem, see an eye doctor to get the correct prescription for your eyes and the best treatment options.
It’s possible that what you’re seeing is a hallucination, especially if it happens at certain times, like just as you’re falling asleep or awakening. These can be caused by many different things, from mental illness to quirks in how you sleep to certain thyroid diseases.
