Have a look at my tutorial below. You can play with the parameters of the Character Movement Component to change the walking speed, the acceleration/deceleration, etc.
What you report sounds strange though. Most scientific literature reports that, when walking in VR, a faster start/stop rather that a gradual acceleration/slow down is much less prone to cause simulation-sickness. This mimics how we walk in real-life, where we quickly reach a steady-state speed and stop almost in place. The same goes for rotations. A quick snap rotation (by 30 or 45 degrees) is easier to get used to than a gradual constant one. Anyway, it is always good to experiment and see what works best for you.
