Perhaps there's a misbehaving add-in. Open Outlook and check your add-ins. Disable as many add-ins as possible. Re-enable one, and use Outlook for a while. If Outlook runs OK, re-enable another add-in. Continue until you've identified the culprit. Alternatively, you may discover that some of the add-ins are for applications you're no longer using. No need to re-enable those add-ins.