VR is more demanding.
You need to do two things:
1) Compare the hardware requirements necessary with respect to both the VR and PC-Gaming environments. Most applications provide some list of Minimum, Recommended, and Best with respect to hardware. You do not want "Minimum" and you want as much "Best" as you can afford.
2) Tally up the wattage requirements of all installed components and add 25%. How close is that total to 350 Watts?
My thought is that the PSU is not up to the task of handling a VR hardware configuration. Especially if the PSU is old and/or has been intensively used for gaming purposes.