My toddler (3yo) recently started acting like a baby, is that regression or not really a problem?

So recently, my toddler began to act like a baby at times - meaning, not talking, running around making baby noises with his tongue out and flailing his arms like a baby does.He knows how to talk decently for his age, but has started doing this and went back to grunting for things. His sitter recently began caring for 2 additional children that are babies, so my wife and I think that it's because of this that he acts the way he does to get the same type of attention a baby does.Would this be something to truly be concerned about? via /r/Parenting http://ift.tt/2rm96MU