Looked up & raised my right arm to reach item on the top shelf, started blacking out until put arm down& head straight. ate full breakfast shortly b4.

That can happen: Extending your neck backward a bit too far and stretching at the same time to reach something on a top shelf can put your autonomic system into a bit of overdrive resulting in what is called a carotid sinus syndrome. The result is a drop in heart rate, a dilation of blood vessels, lowering of blood pressure and decreased blood flow to the head. Don't stretch and reach at the same time! Cheers!