OK guys....
I've been inside the case and gently cleaned out the very small amount of dust build-up there, and also gently applied pressure to the memory cards into their sockets.
I've restarted the system, and it lasted about 3 minutes before again rebooting, so I took your advise and tapped F8 during the restart, got the blue page which asks, "Do you want to restart normally" and selected the line which went something like " Don't automatically restart at the next system failure" and went ahead and restarted the system.
It started normally, except the Firefox browser page didn't come up when selected, though all the bookmarks were still able to be selected.
I also then went into the start menu and found that the automatic restart selection was already unchecked.
Anyway, about 7 minutes later it again failed, and amazingly, it automatically restarted!
Any more suggestions?
