When I try and start the car you can see that the battery is not dead, because the lights turn on; but it doesn't make any noise...not even a clicking sound. And what really gets me is, that it happens randomly...not all the time. I took it to the dealer, but they couldn't find anything wrong with the car. Any input is appreciated.

THANKS

Just because the lights come on doesn't mean the battery isn't dead. ;)

Check the charge state of the battery. Should be 12.0-13.0 volts. If it has good voltage & when you turn the key over it does nothing, then the power isn't being transfered to the starter. It could be an ignition switch issue or a starter issue.