Truck shuts off then turns back on while driving

This sounds very much like an engine controller issue. Basically if the ignition shuts off or stops firing the spark plugs then the engine will stop running. However, if you are still in gear the drive-train can remain connected to the engine and that means the pistons will continue turning. If that is the case, all the PCM as to do is start firing the plugs again and the engine will start running again.

So if I understand the issue properly, if the engine shuts off driving down the road or sitting at a stop light and restarts "by itself" then that is an ignition issue. So that means we need to look what controls the ignition which is the ignition switch and then the PCM.

If the dash does not "restart" like when you are first starting the vehicle, I would go ahead and replace the PCM.