Surging in 6.0 Excursion low speed

I have a 04 X and it has about 18,000 on it. It has run fine until the past week. Twice in the last week when I went to drive it at low speed from a stop it stalled. The rpm was irregular with the motor picking up RPM to maybe 2000 and dropping down all while the pedal was held steady. Any suggestions? It's going to the dealer but was looking for some experiences. It has no reflashes and runs fine once it stopped after 1/2 mile or so, then it runs fine even after shut down and use today.