Flashlight comes on for no apparent reason

I have a Samsung A5 running Android 8. Every so often when I pull it out of my pocket the flashlight is on. The screen will be locked due to timeout and there is no indication that I somehow pocket dialled it. This doesn't happen often but it is totally wierd. I suspect that this may be caused by inadvertent use of some physical shortcut or hack that turns the flashlight on, but I have searched carefully and have not found it. Can anyone offer some ideas?