I found this on civ 4.
Static images were 30fps, and there was jerkiness when moving the map which soon changed to 60.
What I think was happening was that the card was detecting a static display and reducing the frame rate to conserve power.
I went to the nvidia control panel and changed the settings for the game.
I changed power management mode from adaptive to prefer maximum performance.
I also changed maximum prerendered frames to 2 from use app 3d setting.
I suspect that only the power setting change would have been sufficient.
Regardless, the problem is fixed, and I get a steady 60fps which is the limit for the game.