This sounds like a torque converter issue since it is shutting off, but we need to start with checking the fluid level and condition.
Below is the process on how o change the fluid and filter which is what I would do if the level is a little low or dirty.
Let us know what you find with this and we can go from there. Thanks
Images (Click to enlarge)
Tuesday, May 4th, 2021 AT 7:42 PM