'99 Tahoe Intermittant Starting?

[Ironhorse]

Problem with our '99 Tahoe just started about a week ago. Wife calls me from her cell phone and says "car won't start." She is at the local Wally World which is about 2 miles from the house. When I get there and try to start it, it fires right up. Does the same thing couple days ago, wife calls says car won't start. When I get there and try it, fires right up. After talking to her, ( gotta' understand she is not mechanically inclined at all) I find out the Tahoe does roll over, cranks good but will not start. This morning it done the same thing. Would not start after sitting overnight in the garage. Rolls over and cranks fine. Would not start. After sitting for about 30 minutes or so I try it again and it starts right up, idles fine. Shut it off and restart several times with no problem. Engine is a 5.7 (350) with about 76,000 miles on it. Any ideas what to look at? Newer computer controlled engines are not my strong point. More to the old school points, carb setups.