Dizziness/lightheaded and weak during a jog

I go running most evenings after work with my brother but tonight about 15 minutes into it I started to get light headed and felt like i might pass out, we stopped jogging and walked for a while and thought I felt better so we started carried on a few more minutes, we got to a steep hill and we always walk down it and I started to feel light headed again and my legs were really shaking like jelly while walking down and felt like I would not make it. At the bottom my legs started to feel better and we walked a little way more and then ran the last 5-10 minutes, my legs still felt weak but not so shaky like they did, back at my brothers I had a snack and water and felt a lot better.

Should I be concerned or could it be something simple? I had two meals before so I don't think it was under eating but I may have been dehydrated, of course now my HA has kicked in and I have jumped to heart problems etc.