[Aleki]

I'm pretty certain it's radio related. Keep an eye on the signal strength next time it does that and you might see what I mean.
I live in a well insulated house, and I find my Ev signal bounces from full to 1x every so often. It usually illuminates the screen when the phone reconnects to Ev.
I suggested to use the lock-screen so you dont accidentally dial out. Plus, the screen blacks out under lock.