Various examples and schemes pertaining to on-demand network configuration of vehicle-to-everything (V2X) user equipment (UE) autonomy in New Radio (NR) mobile communications are described. An apparatus implemented in a first user equipment (UE) receives a signaling from a network node of a wireless network. Based on the signaling, the apparatus operates simultaneously in a network-controlled mode and an autonomous mode such that: (a) the first UE operates in the network-controlled mode with respect to resource allocation on a first sidelink with a second UE, and (b) the first UE operates in the autonomous mode with respect to resource allocation on a second sidelink with the second UE or a third UE.