It could be related to Steams 'Cloud Sync' feature. Try disabling it in the game properties. Could even go a step further and disable Steams 'Overlay' feature also... to test if that resolves the freezes. Also, in some other game discussions, I read where some had this sort of issue cuz of Steams Music player running in background while they were playing. Double check your Steam--Settings.

There's actually quite a few things that could be going on--mainly background processes--that could cause this sort of issue in games. Either Windows apps or even some Steam settings. So, it's hard to know what might be your issue. You could do a search online for 'Optimizing Windows for Gaming' which should give you some decent links that would help eliminate some background junk.