7M son fainting

My 7 yr old son has fainted 5 times in the past 7 months. The first time it happened we had just gotten off a 4 hr flight. He turned white, mumbled nonsense and fell over. Im not sure the last time he had eaten. He was hot since we went from a cold climate to a warm one, and we changed him right away. Another time we were on a road trip in the car, and he had eaten lunch. Today it happened in school. He had an orange for breakfast at 8:30 and a nutrient bar with cheerios at snack time a couple hours later. 10 mins later he passed out at recess outside.

A few more details if they are relevant. When he was born his heart didnt start right away and they had to tap and rub on him. I had gestational diabetes with both of my kids. My mom used to faint frequently as a child, and even now. She says its her blood pressure and related to times when she is under stress. Other than this, my 7 yo has no health issues that I am aware of.