I had a similar issue a few months back but instead of it happenin periodically it just happend out of nowhere. I had driven to work one morning and when I left to go to lunch, nothin. Everything turned on like you guys are sayin but it would not crank at all. I called the dealership and they told me that my key had gone bad so I ordered a new key ($185 my cost). That was on a Wednesday and they told me that if I ordered the key that day before 2:00pm that I would have it Friday so we pushed my car into the shop at work and there it sat. Friday came and they said that the key didn't show up and that it would be Monday before I would get my new key so I got frustrated and took my key apart. Well my key didn't go bad but the chip inside had moved too far back (away from the key cylinder). I had adjusted the chip and moved it closer to the key cylinder inside the key and put the key back together and it started right up. I have never had another problem with that key again, now I just have two keys that work. Don't know if that is the same thing with your guys issues but I thought I'ld let you know what my issue was and see if maybe it helps you out. Hope it helps.
19" Rims, One-Piece Projection Headlights, 10000K HID Kits on Low Beams and Fog Lights, Clear-Smoked Side Markers, Debadged, Custom Audio/Video System