Any Ideas On Why My 2004 Burb With 6.0 Would Require Cranking 10-15 Seconds-then Shut Off Switch-then Crank Again & Then It Will Start? This Only Happens After Filling Up Gas Tank

Check fuel pressure and post back readings.

Are you having cold weather? If so then it is most likely caused by your fuel pump case shrinking when you put all that cold gas in. When the case shrinks (because it is worn) it causes the fuel pump to bind up and not pump as efficiently as it could.

This is just the most likely cause in my opinion

thanks guys-does this hot or cold weather- try to get back with pressure readings thanks again