2005 Chevy Silverado 05 Silverado z85

I have an 05 silverado Z85 with 79,000 miles. Recently, I pulled into the parking lot at home and while listening to the radio it simply stopped idling. I said huh, I tried to crank it but it initially would not. After a couple minutes I tried it again and it cranked right up and it ran fine for a week. One day after work I was driving home and it started, not so much spitting and sputtering as reving up in quick intervals before it finally stalled out. Same story as before, would not initially crank, but by the time they got their to towe it, I was able to crank up and drive it up onto it. I took it to a mechanic, he let it idle for he said 20 min and never seen anything wrong. So I took it home cleaned the the throttle body and changed the air filter in hopes it may be something simple. Drove it a couple more times and same story. In all this time the check engine light had never come on until today when I cranked it up. I am gonna run a diagnostic on it this weekend, but I was wondering if anyone had any suggestions or oppinions onto what the problem may be.