It shuts off just by getting up from the seat? It should only do that if something is running, like mower PTO or rear PTO. If nothing is engaged it shouldn't shut down, you should be able to get on and off while doing loader work.
On mine, sometimes it will want to stop when I get up and I find I have to move the PTO engage lever - move it back toward on position a bit (not enough to even engage) and back to full off. I'll give it a bit of a push to the off position. I need to clean the switch up a bit so it doesn't do that - had to do it before. You might try that.
Interesting, I'll have to experiment and ensure I have it in neurtral and that the PTO is fully disengaged.