Are these incidents happening when you've just gotten up? Then low blood pressure is a possible diagnosis. 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, make your legs and arms feel rubbery, 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.