There are two possible causes for motion sickness. The first one is an overall low framerate or lagging. If the VR headset is not able to display around 90 frames per second and eye, this may confuse the brain, and it is probably not even recognizable! To ensure a proper playback in VR, you should make sure to use it with a proper graphics card. Please see our Hardware Requirements for an updated list on recommended graphics cards for VR capablities.
If you're already using a graphics card suitable for the job, you can still easily create projects so complex that they might overwhelm your graphics card. If you try to view a large, highly detailed project with high resolution textures, lots of lights, or lots of geometry in VR, this may lead to lagging - in turn causing motion sickness.
The second possible cause for motion sickness is a very natural one, and there is nothing to be done in terms of computing capacity in order to prevent it. It's simply caused by moving. Some people don't feel well if they are moving in 3D space, but standing still or sitting in real life. This tricks their brain to feel as if they're constantly falling or losing their balance. You can overcome this by switching to an Xbox controller to move around the project, as well as chewing gum to relieve nausea.