Ok here is the result.
I am have to go with the window reflection for now.
The drive is on the south side of the house and there are four 2'x3' Anderson Low E casement windows about 12 feet above the driveway grade. There are trees within 20 feet of the house to the south but many have lost their leaves.
I set up a time lapse web cam taking a photo every 20 sec and creating a movie that spans from 9am to 4pm (about 1min).
On day three I found the sun spot I was looking for. It came from one of the windows and created a focused hour glass shaped glare spot that passed through where the truck usually sits.
I examined the windows form the outside and the distorted reflections of the trees indeed indicate the glass in the window is concave and acts as a focusing reflector.
While I haven't got temp readings with a surface thermometer this is lending a lot of credence to a sun / focus effect. Thanks for all the input I will post if something significant develops to support or change the theory.
Bob