New finding,
When I use this:
https://docs.unrealengine.com/latest/INT/Platforms/SteamVR/QuickStart/2/
and in step 10. I use 0 Z height /0,0,0/ :
…10. Select the Player Start and position it so that the center of the Player Start is just above the Static Mesh used for the ground. In this example we used a Z height of 1.0 CM for the Player Start.
…everything works fine.