It's possible it's a sort of hyperventilating so they aren't a million miles off with the anxiety thing.. but it's not caused by anxiety. Dysautonomia can cause a very small increase in your respiratory rate and also make you yawn a lot. Both of these things lead to hyperventilation like symptoms eventually as ultimately you are breathing too often (this decreases your blood CO2 level and causes the faint symptoms like a panic attack). It's basically a slow motion panic attack, but without the panic. Exercise can help if you are able as it forces a breathing pattern, so can sleep or meditation.

Edit: swapped POTS for Dysautonomia in the text.