Thanks for the answer!

I play the game in the borderless fullscreen setting, so I'm always using alt+tab to switch between windows of Spotify, Chrome and the game itself. Perhaps the problem starts right after alt-tabbing, but I'm not sure. As for the areas of the game where it happens, it can happen anywhere. Most of the time, I'm just going from one place to the other to complete a quest when the stuttering begins. The only pattern I can think of is the use of alt+tab.