Silverado’s for the last few years have left the factory with packing grease on the motor instead of shipping with oil due to epa regulations, the dealer is responsible for stripping excess grease upon receiving it at the lot. Sometimes the mechanics tasked with getting this grease off the motor are less than thorough. While the engine runs and heats up it makes the grease thin and runny causing it to basically get blown all over the place by the fans and belts and can get on electrical connections causing power to not get to where it needs to go, ie vehicle turning over but not starting right away. Sometimes the engine light will come on temporarily because the vehicle computer knows something wasn’t quite right but won’t give a code because it doesn’t know what’s going on and eventually goes back off after starting it up successfully a few times
