Slow Unresponsive Outlook

I'm posting this problem again, because I still haven't
solved it.
My Outlook suddenly takes 10 seconds to open and a further
20 before it responds to mouse selections. It used to be
virtually instant.
I have not knowingly fed it with a large amount of data,
or changed any settings.
I have tried "Office Repair", but it made no difference.
In reply to my earlier posting, Andreas asked if messenger
was turned off. It is, because I don't use it. Turning it
back on made no difference.
Can anyone suggest anything else I can try please.
Regards
Don Bowyer