Ok, I think i got it sorted. At least I was playing this night for 2h without any Jitter at all. As I have seen using the Debug Tool that the Jitter occurs when FPS are between 45 and 90 I played with Ctrl+Numpad1/2/3/4.
Ctrl+2 seems to lock it at 45 FPS. I don't get any Jitter, I don't see other strange effects that many here describe when ASW kicks in. It just seems to work smoothly on my machine now. I hope it stays this way.
Been in Stations, in the menues, on planets and Settlements...
980 GTX mildly Overclocked
ASUS Z170 Board
i5 6600K OC @4.2GHz
16G Ram
Settings 0.65 SS, 2.0 HMD Image Quality, Bloom off, Blur Off, Shadows medium, Occlusion off (makes no difference if off or high), the rest high, some even ultra.
Also I installed the latest Nvidia drivers released two days ago.