Stuttering/stammering

My 2 year old just started stammering. It mostly happens when he’s really excited about something and usually just with the word that. Comes out th th th th that. It seems like he’s just stalling until he can figure out the next words he needs to use because his brain is working faster than his mouth - he talks a lot, has more words than I can count, and puts together sentences well. Has anyone else experienced this? It sounds like it’s just a normal phase and the pediatrician just told me to keep an eye on it and we can discuss at his 3 yr check up if it hasn’t improved.