Hello. I have been through your questiin and understand your concern. The complaints you are experiencing are quite common and are reported when standing up very fast. This happens because for that short moment there is less blood going to your head causing these symptoms. Generally you should not worry. Drinking plenty of water and getting up slowly should resolve this. But, if it persist and becomes troublesome then you should consider orthostatic hypotension. Basically, you should get your blood pressure measured by your GP while being sitted and once you stand up. This would just confirm such an eventuality. Still, I dont see anything to be worried about. Drink plenty of water. Wish you the best health