[94 Jimmy]

How does the engine sound when your trying to start it, does it just crank with no indication that it's trying to start, or does it seem to be almost but not quite ready to run. The first would indicate no spark or no fuel, the second would indicate you have both, but not enough of one or the other.
Get a can of starter fluid at the car parts store. If it won't start on starter fluid you don't have any spark. This is a quick way of checking if you are losing spark or fuel pressure. It's not a fix, just a diagnostic tool.
Also Autozone and other parts stores will read your computer codes to see if any are set. An intermittent failure will often not set the MIL (Check Engine) light.
When did you get a tune up last, if you have over 60 or 70 thousand miles the oxygen sensor could be bad and causing the engine to run rich/lean and cause poor starting when hot.
Just a few thoughts.
Good Luck
94