Hi Tom. Have you added anything extra to your front page that might be slowing it down? ( I worked out your school by the way and I see you do have a busy Moodle front page, although perhaps it worked fine before and you haven't added anything)
Moodle 1.9 - random issue possible hack?
we had added some pictures but I have removed them. I think also if it was something like that it would be slow all the time not just random times for a bit. The front page has had this type of design for a while.
It makes me think it is either the antivirus or some sort of process updating etc.