Fortunately for the users, but unfortunately for troubleshooting, the issue is sporadic. The server is currently sitting on 16GB of ram, so we're looking at 2.5% usage or so? What usage would you consider to be abnormal?
The Outlook clients are the only ones being reported. There is very little webclient usage but I will check that specifically next time it happens. I'll also check the w3wp memory usage if it occurs again.
Are you referring to w3svc on server? I haven't noticed anything funny with it when I've had to reset IIS, I will also keep an eye on that next time.