With Chrome, as well as probably any other browsers, if the browser starts running slowly, check the plugins (extensions) that you have installed. Each of the extensions is using memory and CPU, and adds to the time it takes the browser to start up when you launch it.
For Chrome, there's a button in the top right corner with 3 dots. Click it and then go down to More Tools-->Task Manager, it will show you how much memory each browser tab and how much each extension is using.
And you can disable / uninstall extensions my going to More Tools-->Extensions.