Kobo Aura won't stay switched off!

I mentioned this issue in another thread but it probably should be on a new thread rather than tacked onto then end of another one.

New Aura - only got it today. Working fine (after a few pointers from the forum - thanks for that). The problem is it won't stay switched off! I flip the red button. Screen clears. Leave it 10 seconds and the damn thing starts up again!

Any ideas please?

Thanks

Steve