2006 Ford Fusion Failure to turnover when key is turned on

In the past year less than half a dozen times when attempting to start the car it will not turn the starter motor over. The battery is fully charged and after some delay upon attempting again the car starts as normal. The last time it did not start until the following morning. It has been taken to the dealer but has not reacured while at the dealer so they tell use they can not determine the problem? Is this a common problem with this model? It seems to me it is likely in the ignition switch or wiring? Please advise thank you.
Tom