I m a 19 year old male (194 lbs/5 10 ) who recently (around a month) decided to do daily walking exercise to put an end to sedentary lifestyle. I ve been feeling dizzy while doing it for the last few days, though, even though it s just 5 minutes (I walk around 20 minutes daily). What s the possible cause of it? For your information, I have GERD, and have had echo, chest X-ray, and head MRI done two months ago and everything was clear.