System is automatically rebooting after updates

You are most likely experiencing the plymouth issue that a lot of people are currently experiencing as well. There is another thread about this: Update hung up on post trans update

tl;dr: plymouth package is broken and it’s the thing causing issues with updates. You have 3 different options to do here:

  1. Stop the plymouth service before updating your system: sudo systemctl stop plymouth-start.service
  2. Remove all plymouth and libply packages from your system and lock them (if you would like to keep plymouth on your system, don’t forget to remove the locks after you update): sudo zypper rm libply* ply* and then sudo zypper al libply* ply*
  3. Wait until the bug is fixed.

(Sorry if formatting is bad. Posting from phone sucks)