While sleeping usually at my left side, i wake up suddenly from sleep grasping for oxygen, i feel as if lungs got blocked, after opening eyes, everything gets normal. i don't always snore but this issue is now recurrent, i am not even overweight?

It's hard to say for sure, but its possible it's related to a form of sleep apnea. It may not be the most common presentation, but nature behaves differently for different people. If it's bothering you, I'd talk to your doctor. They may want to take a chest x-ray, and possibly send you for a sleep evaluation study. I wish you the best of luck!