99 AU stalling.

[Crash Lander]

My 99 AU, on first start of the day, starts, the revs start to drop, then it
stalls. Turn the key again, and all is good for the rest of the day. The car is not converted to LPG.
Sometimes it does it at the end of the end of the day when I'd ready to go
home, but it's fine at all other times.
I had a quick word to a mechanic, and he said it could be the BCM (Body
Control Module) that needs to be reset.
Any idea how I do that?
Any other ideas on what it could be?
Other work I'm doing on it, that are unrelated is, I'm replacing the
tensioner and pulleys this weekend, as well as changing the oil and plugs,
so it's a pamper the car weekend. I'd like to get this stalling sorted out
while I'm working on it. I initially thought it could be a coil pack on the
way out, but the mech I spoke to didn't seem to agree. The car has done
about 235,000km.
The car in general never skips a beat, gets fantastic mileage, and is
probably the most reliable car I've had.
Brakes need doing in the new year too! ;-)