When starting the engine my Z-E3215 MkII switches off and reboots.

Answer: If the voltage supply drops below 9 V, your ZENEC device will shuts down automatically to avoid operation faults and inclomplete loading of software parameters. This is a device self protection mechanism and not a defect. You may, however, check the electrical installation of your vehicle (battery worn down, bad or corroded ground contacts / connectors, etc.).