Wife was backing her 2018 Silverado 1500 out of the drive which is on a slight down grade, so I don't now if it was actually under power or not but when she got in the street to pull forward/away, it wouldn't move, forward or backwards. She comes running to the house to get me as traffic is blocked and the truck won't move. I get in it and try both reverse and drive and also nothing. I shut off the ignition and restart it and put it in drive and it runs right up the drive as if no problem. She said it was having some strange feelings the last time she drove it but now I am afraid for her to drive it since this failure. Since I am not mechanically inclined my thoughts are that it must be computer related instead of mechanical since it moved after shutting off and restarting. Has anyone had anything like this?

 

Would suspect the vehicle computer received a signal that caused it to place the Powertrain computer in what is called limp mode . This is done to prevent further damage and still allow a vehicle to be driven to a service facility. If the fault that triggered the problem is not present after the key is shut off ,the computer will reset until the next time the fault shows up
.A check for any codes in the computer might be present and provide some direction as to where to start looking.
Sometimes it is something simple and other times it can be difficult to find.
In any case a capable scan tool will be required to start looking for direction and a good shop should be able to help here.