Can you please mentioned either it occurs at once or multiple times.
till meantime try this.
Start Outlook in Safe Mode. To do this, open the Run box, type outlook /safe and hit Enter. If it runs fine, you may want to check the installed add-ins. Disable some Outlook add-ins and see if that helps you.
Click File menu > Options > Add-ins > Go button besides Manage: Com-in Add.
