Ill-fitting shoes? Best thing would be to go to a running shop and they'll set you up with correct shoes with the correct gait. TBH though, i experienced similar pain, albeit in the calfs of my legs and shins, when I started running and I imagine it is just your muscles that are not used to it adjusting to the new movement. Try running on softer ground such as grass, or sand if you're by the sea, rather than tarmac and that should make some difference. Also give yourself time to heal in between runs, a few days at the beginning, worst thing to do would be to go everyday and hope it gets better. Good luck