(VR Rift) Happens to me when in creative and trying to land 100% of the time, switching to survival doesn't help. It randomly happens when jumping out of water. I've been launched into the air by a phantom or whatever those horrible flying things are. Only thing that fixes it is exiting to main menu and entering world again which can then trigger a bug where the screen has a seizure whenever I move my head even a little bit.
I'll turn that off (if it's on) and see what happens.