The switching on automagically thing as reported by OD is a fault in one of mine too. I just ignore it and never turn it off. If I was worried about the minuscule power drain from my thighs of Hoy, I'd do some training so I actually had thighs of Hoy. I am, obviously, thankful that the fault is turning itself on not off.
The not being to turn it on except when moving is a different, and far more common, problem. I don't think they're related: one's some sort of loose connection somewhere, the other's shoddy capacitors.