/*This is not possible because it’s not allowed to execute this action without user input (as the console says).
You could use a info or start screen and when the user closes this screen, you can enter VR in the same moment. But the user has to click something.*/
I haven’t read your last sentence sorry. It is possible if you were already in VR before.
You have to grab the vrdisplayactivate event from your browser:
This ‘counts as’ a user click and you can enter VR when this event gets fired.