svchost.exe isn't a service itself, but rather, as the name implies, it's a host for other services. In other words, it's not necessarily Windows misbehaving, but a particular piece of software you're running.

Find the PID of the svchost.exe process that's eating CPU in Task Manager. Then go to the Service tab of Task Manager and find the service with that PID. You'll have your actual culprit of what's eating CPU. It COULD be a Windows service that's acting up, but it's just as likely some 3rd party service.