Why does my vision sometimes go black/fuzzy?

Is it when you've just gotten up that this happens?

Low blood pressure (orthostatic hypotension) is extremely common in young people. It can make your vision dim or temporarily disappear, starting at the edges of the vision field, make you so dizzy you can't walk, or make you faint. Usually it causes no health problems beyond the potential for injury when you fall in a faint.

Blood pressure tends to rise naturally in the middle adult years.

Common factors contributing to low pressure ‘incidents’ including dizziness or fainting are heat, first day of your period, getting up quickly, getting up from lying down, dehydration, and not eating recently enough.

You may find a near-faint resolves almost immediately if you either lie down or sit and put your head between your knees. This gets oxygenated blood to your brain the quickest.

People with low blood pressure should get in the habit of moving around before they get up. It's a pain, but worth it considering how easy it is to break a bone when you faint and fall badly.

It is called Orthostatic Hypotension. There are various causes. What happens is your blood pressure drops rapidly when you stand up and your body stops getting blood all the way up to your brain. So that blackness is the blood draining out of your brain for a monument. Your body is taking slightly too long to adjust your blood pressure.