Jeep grinds going into gear?

Like you say there's nothing in an automatic that can make grinding noises. Try unplugging the Neutral safety switch and see if it stops. It's wired to the starter relay and might me kicking the starter on as it passes through neutral

A hard one to tackle as not very much info is given so based on that I will do what I can for you

1) Low tranny fluid

2) A misadjusted shift linkage could do this as it is not letting it fully engage into its gear detent.

3) Bad pump and pressure out put

4) Bad bearings

5) Worn planetary gear and bands or drum

6) Worn / malfunctioning solenoids

7) Blown valve body gasket or warped valve body

You can check the shift linkage to make sure it is fully engaged the rest unless you have the tools and abilities is best to have a good shop that know your type of tranny is best as there are many other parts and or reasons that this can happen but almost all will require a partial teardown or specialized tools for testing.

On a side not to keep driving it this way could easily do more damage so it is best to have it looked at and checked out sooner then later

Good luck and hope this helps even thou it’s most likely not what you wanted to read.