Well, if it's only just started then I think we need to look at stuff that gets updated regularly.

1. Security software
2. Browsers
3. MS Windows.............and we have just had a patch Tuesday?

Please get a copy of Belarc Advisor and let it update and run. Scroll down the bottom and look for any updates with a red "X" against them. Uninstall and reinstall these patches.

If it isn't a screwed up Windows update then try closing all browser windows and tabs and see if the same thing happens.

Is your processor showing a high level of activity during the idle period? I use System Monitor II by Igogo to look at this.