First of all, have you installed drivers? Those really helped me. Just google Intel drivers and download.
Two, what are your settings at? I'm talking about anti aliasing. Best option is to turn that off.
Three, go to start up options in steam, and type in "-vid -high", It will take away the video at the beginning and automatically set CS:GO to a high priority on your computer.
Let me know if it works or not.
-Hayden