|If the CPU usage just spikes and comes down again, then you are experiencing something normal. Every web page and link you click on needs to be 'built' on you screen, every image, moving graphic, web link, text, every cookie that asks your CPU to do something as well as your antivirus needing to scan everything that is loaded uses CPU power (especially if your graphics are onboard) so you get these spikes. Add that to other programs you may have running in the background (even if you do not know they are there) and those spikes can get fairly high.|
If you are worried about a possible infection then scan also with Malwarebytes once a week or month just to be sure as well as whenever your computer begins acting unusual.
If you think you are beginning as too high an idle point then remove some programs from starting with windows with msconfig Start Tab, all you typically need is to leave is all Microsoft processes and your antivirus program, OK and restart the machine.
You have to be a little bit crazy to keep you from going insane.