This "phantom locking" issue on a 1995 Infiniti Q45 is a known electrical quirk, usually stemming from the fact that the locking system is "negative trigger," meaning the locks activate if a specific wire simply touches the metal chassis (ground). The most probable offender is the wiring harness located inside the rubber accordion boot between the driver’s door and the car body. Over three decades, the insulation on these wires becomes brittle and cracks. When the engine vibrates or the door moves, an exposed lock wire can brush against the metal body, instantly triggering the locking mechanism regardless of whether the keys are in the ignition.
If the door jamb wiring appears intact, the next suspect is the master window and lock switch on the driver's armrest. The internal contacts in these switches can loosen or build up carbon over time, causing them to "bounce" and create a momentary connection from engine vibration alone. A simple way to test this is to unplug the master switch while the car is running to see if the phantom locking stops; if it does, the switch likely needs to be disassembled and cleaned or replaced entirely.
You should also check for any old aftermarket alarm systems buried under the dashboard. In the 1990s, dealer-installed security systems like Viper or Clifford were common on luxury cars, and many included "passive arming" features or ignition-controlled locks. If the alarm’s main control unit is failing, it may send erratic signals to the door actuators. Less commonly, the vehicle's factory Smart Entrance Control Unit may have failing capacitors, though this usually presents with other issues like flickering interior lights. Until you identify the root cause, it is critical to keep a spare key in your pocket or roll the window down slightly whenever exiting the running vehicle to prevent being locked out.
