Steering wheel shaking outta nowhere @ 70 - HELP

I have had my Optima (2010) for just over a year. Wednesday on my way home from work, I got on the highway, was cruising at 70 for about 5 minutes and then my steering wheel started vibrating ridiculously! I turned the cruise off using the button to see if that would help, slowly started to loose speed (makes sense) but I couldn't maintain my speed or speed up. The pedal felt normal, but it was like the engine wasn't getting the message and by the time it did, my foot was done trying and it sounded like I was standing still trying to screech my tires. I pulled over to the side of the road - practically stopped on a dime (it was as easy as ever). "ESC OFF" was on the dashboard, and my car reeked from my brakes getting too hot - but what happened?!?!

Towed my car to the dealership, they sent me home after balancing my tires and told me to put new brake pads on and replace the rotors - they didn't know what happened. But it seems like something had to have happened to cause my brakes to get hot... they don't just get hot for no reason! They said there was only minor vibrations when they applied the brakes. I got major vibrations without touching the brakes. ANY IDEAS? =( Everyone keeps saying something must be wrong, but no one has any ideas as to what that might be.

TortiseLover, have you figured out what caused this? Fixed it yet? Very interesting problem I would guess that your brakes locked up for some reason and got too hot, while you were giving it the throttle the brakes were trying to stop you.