Engine shuts off when transmission is shifted into drive or reverse?

Does this happen all the time or did it just happen once?

The best thing to do is start with what codes you have.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

More than likely you will have some gear ratio codes as I suspect the torque converter is stuck on. When you are adding a load to the engine the engine will be pulled down, however when the converter is not released it is the same as if you didn't push the clutch in on a manual transmission when it was in gear and the engine just stalls.

If this is not it then here is a guide that will get us onto the next items:

https://www.2carpros.com/articles/stall-at-idle

Let's start with this info and we can go from there. Thanks