Your 98 GMC k2500 Suburban sometimes will not start for 15 min The security light comes on what causes this and how do I fix it?

You may want to look at the Theft-lock module in the steering column. I am in the process of replacing this unit in my 1999 GMC Burb that was doing the same thing. When the theft-lock module is going bad the unit will start shutting off the voltage to the fuel pump because it thinks the car is being stolen. This a project that takes approx 2 hours and some good tools to do. I advise using your trusted mechanic or the dealer.