My grandson's feet do this too. The Pediatrician wasn't concerned but we were. We asked for a referral to a foot doctor and took him. He got molded insoles that are shaped to his feet, we got good recommendations about what type of shoes to put on him, and he gave us exercises to do on his hips when changing his diapers that we continue to do everytime we can get him to lay down.
Shoes that cannot twist back and forth. If you hold the heel in one hand and the toe in the other and can twist it back and forth then the shoe isn't strong enough, not enough support. Also, higher top shoes like little hiking boots give supprot to the ankles. But they can't hit in the wrong spot and make blisters. So, good strong support shoes. We currently have him in short black boots from Wal-Mart that lace up and have 5 or 6 eyelets.
When laying on his back we spread his knees out with his feet together, the palms of his feet touching. We stretch the knees out as far as comfortable but still keep his feet touching. This stretches out the hip joint and that is usually where the turning in starts. It just continues down the leg.
The doctor won't do anything more invasive at this time. Their bones are still forming and it's not time yet.