2000 Chevy Silverado ext cab, 1/2 ton, 4X4, 4.8 V8. Drove home the other night, not one problem. The next morning, I went to start it and it wouldn't start. Turned over quite well. Sounded like it was hitting on the initial turn of the key, but just a slight sound of a hit, then no hits at all. Each time I turned the key, same result. !/2 tank of gas. 3 week old battery fully charged. Truth of the matter is, it appears to be like a security feature, but I am unaware of any on this vehicle like that. Any suggestions? Thanks.