The version is likely irrelevant, but you're running a month-old beta version, so you should start by either upgrading to the most recent beta version or switching to the current release version (and you should figure out why you weren't receiving automatic updates).
If you're still having trouble, we'd want to see a Debug ID (different from a Report ID) for an operation that was slow and/or a crash.
Unless you've changed app.update.enabled or app.update.auto in the Config Editor in the Advanced pane of the preferences, updates happen automatically on Zotero restart, as long as nothing on your network is blocking update requests (in which case you shouldn't be able to update from Help → Check for Updates… either).
I am not aware of changing anything in the configuration, but on inspection I found both app.update.enabled and app.update.auto were set to false, so I reset them to the default true. My internet connection is fine (cabled 35Mbps) and synchronisation is instantaneous.
Upgrade Storage
If you're still having trouble, we'd want to see a Debug ID (different from a Report ID) for an operation that was slow and/or a crash.
I cannot find any option to automatically install updates. ... ?
It has not happened again since the report I made, but if it does I will get the Debug id. as well as the Report Id.