I have E-120's and had similar symptoms. Initial power up was fine, system seemed to reboot one or both screens with no obvious reason. Reboots seemed to be happening 3-4 times over the span of 30 minutes. Power supply seemed fine, nothing obviously wrong. Checked voltage from alternators, battery connections, battery switches, etc. After some hair pulling and head scratching I looked a little deeper. It turned out to be loose ground connections on the bus bars (one in the transom, one in the console). I disconnected, cleaned and reconnected. Everything has worked correctly since. I suspect you have a bad connection somewhere in your electrical system. I think the shutdown (reboot) is a safety feature when the system detects dirty power (spikes, surges, drops).