Let's say I go in and set the autogrow for the tempdb and templog to 100MB
(for example).

What could cause it to reset itself to autogrow by 1 MB? I know for a fact
that it's happened after, because or caused the "Autogrow of file 'templog'
in database 'tempdb' cancelled or timed out after 0".

We increased the size of both last week and that seemed to help until
something goes wrong...so I'm hoping someone has heard of why it would reset
itself to autogrow by 1MB even though I've changed it. What can I do to
prevent this in the future?

You need to modify the autogrow in the Model database. Modifying tempDB only has a short lasting impact as tempdb is recreated from Model every time you restart the SQL Server service.

You need to modify the autogrow in the Model database. Modifying tempDB only has a short lasting impact as tempdb is recreated from Model every time you restart the SQL Server service.