jljbtm

This morning my 99 K2500 started fine but as soon as i started driving down my road it was hesitating real bad? so i got to the end of the road turned around to hopefully get it back home then all the sudden it smoothed right out and ran fine. I think by this time it had warmed up to operating temperature, but what the heck could be wrong? I used it in the afternoon also and it was fine then too. Oh 215,000 miles. I like to fix these things myself but i kinda dont know where to look for this problem. Thanks in advance for your help/guidance, Jack