For the last few days, when I launch Outlook for the first time since boot up
it opens a window titled "Installing Components for Microsoft Office Outlook"
and in the body it says "Installing: Microsoft Office Outlook feature" with a
progress bar underneath.

Once this is complete the window closes and Outlook carries on as normal.

I have checked Advanced Options and there are two add-ins active in Add-in
Manager, AVG Exchange Extensions and Exchange Extensions property pages.
There are no COM add-ins.

Not quite sure what it is trying to install and what has caused this to
start happening. I'm just worried it might be malicious.