1996 Chevy Suburban sometimes the truck wont start

Electrical problem
1996 Chevy Suburban V8 Two Wheel Drive Automatic 90.000 miles

over the last two days this has begun. No idiot lights come on. It seams as if the truck isnt getting fuel but I am not sure. Like I said sometimes it starts fine sometimes if you rock the truck it starts and other times it wont start at all how do I check the fuel system and if I were to blow through the fuel lines towards the in tank fuel pump might this blow any dirt out of the in tank fuel pump screen or do you have any ideas thanks