I think it remembers the state it was in when you power off the modem (well, that’s what I’ve observed). So if the LTE has been shut down prior to turning off, then it won’t start on the next power on.
I’m running 3.203 based on this post as I need the manual configuration to be remembered.
I just use the buttons in the UI and the hardware button, so after pressing “Disconnect” and then just powering off, the next time I power on the modem doesn’t start. Conversely, if the modem is up and running when I press the power button, the next time I start the device, the modem starts.
Not sure if it makes a difference, but I have the EP06-A modem, not the EP25.