1999 Suburban won't start when it's only been off a short period of time

A few months ago, our Suburban started having issues starting up. Most of the time, it starts right up with no problems. However, when you turn it off for a few minutes and try to start up again, it doesn't like to start. Sometimes it will start up and then die when you shift it in gear. Not sure what to think on this one. It's been 1 minute to 15 minutes between when it's turned off and when you go to restart it and the same thing happens. If it's longer than 20 minutes, it seems to do just fine. No problems starting at all. Any suggestions would be helpful!