I exercise occasionally once in 4-5 days for half an hour. Today I ran for 5 minutes on the treadmill inside a room not too well ventilated. Afterwards I walked at brisk pace for about 500 meters. 10 minutes that I was having breafast, while in course of breakfast I felt dizzines so much so that I stopped taking breakfast came out of the restaurant and sat in the open under a tree shade. After breathing for a while it felt Okay and I walked back home. Is this a symptom for something grave? What I should I do to ovrcome this at least its recurrence?
As with all health questions, the answer is to see a doctor. Dizziness could indicate that an insufficient amount of oxygen is reaching your brain. Causes of that can be as benign as being very winded or as serious as a heart problem. A physical examination by a doctor is the only way to know the cause is benign.