D.R.
Hi N.,
It's so funny that you should ask about this because I was just reading a book from Focus on the Family regarding child development from birth through teens (I was specifically reading the 3-4 year old section for my preschooler) and it mentioned that it is a normal thing for a 4 year old to begin stuttering and that it would pass. I believe that the book said to keep an eye on it, but there's no need to see a specialist as long as it goes away in a couple of years! Just my thoughts!
D.