Warwick is right, it might be Avast.
Mine started to act up after a update some weeks ago.
I downloaded the new one, uninstalled the old one but it kept 1 service in the pc with almost 99% cpu usage. (Avast behavior shield)
I then used the uninstall tool and installed it again. It worked fine after. Even the behavior shield is now running at 0% most of the time
You can download the tool here: https://www.avast.com/uninstall-utility