While driving down the highway, a message popped up stating not suitable to shift and I lost all acceleration and could only coast. Luckily was able to coast over to the shoulder, where attempts were made to shut down and restart vehicle. Second message came up stating reducing features to save battery. Was unable to restart and a tow was requested. Dealership reported it was unknown why or what caused it but engine was locked up. Engine only had 19k on it with just me as the owner.when purchased brand new 17 months prior.