Running is tough. Especially first thing in the morning when your body is still dog tired and stiff. And so, this is how it feels.
There are a few phases of running I've found. First is the one starting. I find its my abs and inner thighs that strain initially. Your ankles hold their breaths. But this is also where you say to yourself, "c'mon lets get at it!". The second is the stiff but gradual easing acclimatisation to beginning as you start pushing forward - here you also start getting used to the cold. At this point you're one your way.