Try the following:

1. In the Misc tab of Settings, uncheck the boxes for Camera Shake and Immersive Camera. In the graphic settings, turn off Motion Blur.

2. Play with back lighting behind your monitor against a pale wall. Make sure to sit about 2.5 to 3 feet away from your monitor if your monitor is about 27" or smaller. If you're playing on a larger screen, like a television, then you should sit even further. Lastly, make sure you're not sleepy or tired.

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For others who don't know what this is: This is simulated motion sickness that usually happen when the camera is attached to the character. So when your character has sway or head bob, then the camera sways and bobs with it. When you're walking in real life, you don't feel motion sick, because your brain works in tandem to your movement. When sitting down on your computer chair, your brain can't process the movement you see with your eyes on the monitor. Thus in simple terms, you get sick.