2000 1500 silverado v-8 5.3. Several times over the last 5 years when go to start, the engine turns over and starts to run but dies imediately, like the electrical path is going open as soon as the starter kicks out. Today when it happened, It started fine but the security light came on. It has done this off and on and most of the time I just turn it off and restart and the light goes away. Today when I went to restart is when it failed to keep running. I have tried exercising the key back and forth, wiggiling the shift lever(automatic) and numerous things. Sometimes it will start--sometimes not. Don't think anything I am doing is making it work. Most of the time if I just walk away, come back in a few minutes, it will start and run fine for weeks to months with no problem. It has happened twice now in the last month. Any ideas?