Have the dealership check the throttle body. I took mine to the dealership on a Friday for what felt like transmission slip. They did a "fix". I drove the car a few days later and the slip was worse than ever (felt like someone learning how to drive a stick shift).
Was driving the Edge on a busy 6 lane section of interstate when the speed begins to reduce on it's own. Luckily, I was able to get the car to the emergency lane without being hit. Car towed to dealership and the throttle body is in the process of being replaced.