heart rate question

I m not running in races as I trail run for the love of the trail and to allow myself to hike long distances. I trail run about 60 miles per month. I am 54..My question is: Occasionally, after about 2 to 2.5 miles, especially going up hill, i become light headed and seem to be losing my breath. I have to stop and stand still, then continue on. And then for the remainder of my run, especially up hill i have to deal with this uncomfortableness and stopping and starting back to the trailhead. Again , this doesnt happen to me everytime, just occasionally. Have you ever experienced this or know what is happening to me ?

Hey I think you should talk to a doctor about that one, especially if it's a newer observation for you.