Possible Causes of Lag?

[wefhqweig]

Ik there are endless threads like this, but I can't find any with a similar pattern as mine and a working solution.
I can usually run the game with maxed settings just fine, no stuttering or freezes. Even streaming/recording I have a steady 60-70fps or 100-120fps in some areas and 110-130 or 150-160 ping. In combat ping stays the same, but my fps may drop, but that's fine, it doesn't effect gameplay and still looks good.
But, I can't figure out what causes me at times to lag so bad. FPS plummets everywhere, and the game is visibly laggy and then in combat(only while I'm actively attacking) I get freezes that last 3+ seconds. Sometimes a relaunch fixes it, but usually I have to restart my computer once or twice then it's back to playing stably.
 

My specs:
Ryzen 5 1600 (Does setting affinity to certain cores improve performance?)
16gb 2400 mhz
MSI GTX 1070 Ti 8gb
Windows 10