After reading reviews, I determined this is a common problem with Whirlpool wall ovens. I replaced the thermal sensor and the thermostat just to make sure. Looks like all I needed was the sensor. $30 is much cheaper than a wall oven replace.
It was quite simple to replace, when the oven is out of the cabinet. I am the person that installed the oven and it and was quite easy to remove.
I am very thankful I found this site. They had parts in stock and shipped right away. I received the parts in 3 days.