Your turtle probable hatched out last summer and overwintered in the nest. I'm sure he just came out. Several hundred miles south wwe are still doing the same. Keep him warm with the basking light and repto min is hte right thing. You never know what happened before you found him. If he just crawled out of nest he will not feed right away. just make sure he can get out of water if needed. I would bet in a couple of days he will be just fine. By the way enjoy those awesome Michigan summers.