2006 Toyota solara transmission problem



After driving for 1.5 hours at 70 mpg and slowing down to get off a ramp the car lost drive and wouldn’t go. The car wouldn’t move! I was able to put it in reverse and park but no drive! (MIleage on car is less than 8,000). After the car sat for 30 minutes it drove fine. Upon driving another 60 minutes on the highway this occurred again. This time nothing would allow it to go into drive. It was towed 100 miles to a Toyota dealer and they can’t find the problem! Can anyone help me?