I once had a phone reboot upon connecting to a specific hotel wifi network, then bootloop until I took it out of range. Sometimes things just break. Military interference seems unlikely; a phone carrier, and by proxy a government with jurisdiction over one can track any phone connected to the network regardless of the software running on it.
It’s useful to immediately save the logs from logcat when something like that happens. There’s often enough information in there to find out why a crash or reboot occurred, or at least what part of the OS was responsible for it.