Minutes into my runs I get a burning in my thighs and legs and I don't know why. I can hardly go beyond 30 minutes of running. I can berunning as slow as 8 minute mile pace and it comes. I stop for a couple of minutes and re-start and it comes back within a couple of minutes. I have done nothing real fast. Just been doing base mileage since arly december. What could it be that I am feeling?