Nothing is running in the background, just Steam. BTW I used its statistics overlay which says that VRAM is used up to 95%. Maybe I should try to increase the VRAM to 8 GB? But then only 8 GB regular RAM will remain.
Yeah, there's your issue all right, didn't realise you were so limited in VRAM, 8Gb is fine to run the game in, but you MUST have as much VRAM as you can spare, if you are under 8Gb that's a big problem.