Jimmy Not Starting

Have a 2001 GMC Jimmy, 6 cylinder 70,000 miles. Occasionally, (every one to 3 weeks) when I put the key in the ingnition, and turn the key to start, there is absolutely no response. No grinding, no starter noise, no click, etc. Nada. I will putz around with putting the key in and jiggling the key in the lock and turning the key on/off for 10, maybe 15 minutes and sooner or later it'll kick over just like it's suppose to. When I put the key in the lock and turn, dash board indicators are activated so I'm assuming the key/lock is OK.

I'm thinking of some type of security lockout or other electrical timing reset based on some unknown factors. Since it happsens only rarely the dealer says if they can't see it, they can't fix it. I'm in constant jepordy of being somewhere needing to be somewhere else the next time it fails. Each time there's the question 'will it start this time'?

Any ideas appreciated.