Sonim offers a unique feature in handset Settings, which allows phones to be programmed to power on and off based on power supply. Reference chart.

SettingDescriptionUse Case
Automatic power ONHandset will automatically power on when connected to power via USB C or charging pins.Handset will power on when it is connected to
vehicle kit or multi-bay charging pins, or car or
wall charger via USB C.
Automatic power OFF (at set time)Handset will automatically power off at the time it is set to power off. If voice or PTT call is in process, handset will power off 10 seconds after the call
has ended.
Handset will power off as scheduled.
Automatic power OFF (disconnected from power)Handset will automatically power off at the set hours after the handset is disconnected from power via USB C or charging pins. If voice or PTT call is in process, handset will power off 10 seconds after the call has ended.Handset will power off when no power is supplied from a vehicle kit or multi-bay charging pins, or car or wall charger via USB C.
Power OFF alertHandset screen pop-up alert appears 2 minutes before the scheduled power off time, with an option to snooze for 10 minutes.Reminder advising the handset is scheduled to
power off, with the option to delay power off for
10 minutes.