Silverado 2002: Trouble Starting

I have a 2002 5.3L Silverado and I'm having problems starting it up. When I turn the key it doesn't start up right away, instead it sounds like it's trying to "catch" before it turns over.
Any ideas? Thanks, John.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.