Hello,
We are seeing an issue where Jira restarts after some plugins are updated. This does not happen all the time only some plugins. I am not sure if this is dependant on the size of the plugin. The last plugin this happened with was Atlassian Universal Plugin Manager.
I am not 100% sure what to look for in the logs. However, we can see that shortly after the plugin update has been initiated that all plugins are then stopped and the server, I assume, is restarted and not crashed.