Toddler play regression ?

mgduke19

hi ladies- I have a son who will be 4 in August. He is an only child but goes to preschool and he's around kids a lot. Recently, he only wants to play with babies when we are at the playground. Then he talks like a baby the rest of the day! He says that he's just pretending but it still concerns me. He was always so outgoing with "big kids!"
Anyone else experience this?