I've been having the same problem since I started playing again in Duviri. DX11/ enhanced and the only thing that "fixes" it is restarting the game. Recently upgraded cpu/ motherboard and the stuttering is much less severe/ frequent in a second by second basis than before as it was basically hard freezing for ~1/10th of a second every few seconds whereas now it's probably 1/20th of a second and happens every 10-20 seconds. Went from an i5 8400 to a Ryzen 7 5800X3D.
Edit: The stuttering only occurs when I'm solo/ host when inside a mission, not in orbiter/ camp. Never happens when I'm playing with others who are hosting.