Shuts off = just stops mowing or engine stops.
Electric PTO switches do burn out after extended use
Some clutches will overheat and cut out if the air gap is too big
JD make a wonderful Technical manual that the average 10 year old can understand which details exactly what every bit does, how it does it and how to test it then how to replace it if found to be faulty .
Costs about 2 hours of a mechanics charge out rate so pays for itself the first time it is used .