Look Ma No Oil

FYI the oil pressure switch in grand cherokee's will shut the motor off with lack of oil pressure.
I bet the one in your mom's is getting ready to fail.
I had one fail on my 99 after the motor cooled off it would start.
I change the switch, and added a "T" and put an mechanical oil pressure gauge in.
Every once in a while the gauge will start reading erraticly but the mechanical one reads just fine.
The switch is on the top back side of the motor but is a real pain to change.