Many children stutter somewhat during toddler-hood and it this age it is considered a perfectly normal part of speech development.
It is not known exactly why stuttering occurs as part of speech development, but one idea out there that makes a lot of sense to me is that they simply get ahead of themselves from excitement or operate more slowly from fatigue at times. I buy into this one because in my own experience, kids seem particularly likely to stutter when in a hurry, tired or super excited about something. I actually think a lot of kids do this from time to time, but it seems that depending on how one measures, somewhere between 5-20% of kids do this at some point in their development.
Stuttering does actually run in families, and contrary to formerly popular belief is not likely to simply be brought on by some traumatic incident. If there is no stuttering in your family history, there probably is no real reason for concern. In my experience it would be a good idea to wait and watch. Don't worry about it too much (don't worry about correcting it), but pay attention and notice when it happens.
Stuttering Answers says:
"2) You are best advised to just observe your child's speaking for a period to assess if the stuttering is getting worse or not. It is not unusual to be in this observation period for up to 12 months. As mentioned, many children will spontaneously recover within that period. Having said that early intervention is most important and stuttering is best treated before the age of 6."
Some signs that there is something more serious going on can include:
- signs the child is tense and the stuttering increases the child's tension. btw - in these situations, the child recognizes the sounds are wrong and it will not help to correct him - but only serves to increase anxiety over the matter.
- Frequency of stuttering and the length of time spent on prolonged sounds increases.
- The child stops talking around certain people.
Most likely, you have absolutely nothing to worry about. Some resources say that getting help is a good idea around age 5, while still others say six. I've had students whose parents sought out help at age 4 so the child didn't have problems socially at school. It seems to me, that if you wait a year or so and the stuttering still persists and especially if its frequency increases, sometime before the age of four is a good time to have your son evaluated (since he is only two now). For kids whose stutter starts a bit later, 5-6 seems to be the standard age.