Car stalls in cold weather

Hi - I have a 95 X300 Xj6 - yesterday i went for a run mid afternoon - maybe 17c and did not miss a beat. I had just checked for codes OBD2 and none. Went out at night and returned home 9pm - ambient temp maybe 5c - car stalled all the way home (short distance only). I ran in the drive for a while and continued to stall - intersting was the door lock lock and unloced as if it was driving. Anyone got an clues. Ill check the Intake air sensor today nad have just repalced the coolant temp sensor. Lock mechanism activating makes me think of road speed ? Any hjelp appreciated. Matt