There are a few areas in Outlook that can be examined for this error. The most common error would be a message in your inbox, formatted as HTML, has a bad JS attached. I am assuming you have Outlook configured to open into your inbox upon start up, correct?
You could temporarily change the start up location as indicated above to "Calendar" (see below) then check to see if the issue continues. If it does not, it is definitely an issue with a message you have received.
I'm not suggesting you leave it changed, just presenting it as a trouble shooting method to narrow the source of the issue you are having.
The other area to examine would be add-ins. Trouble shoot the messages in the inbox as described above, first, and, if that doesn't fix it, we can work from there.