I had the the exact same problem for a long time, also started when temperature was at or below 10c. It gradually got worse with the problem starting to occur at higher ambient temps. Eventually I couldn't drive off without sitting still and keeping the revs high for a couple of minutes. If I drove off straight away it stalled when the revs dropped.
I had the car checked over by an Alfa specialist several times who carried out numerous checks including the engine, earthing points and battery but all seemed ok.
I started tinkering with things myself and one time left the battery disconnected overnight. In the morning the car started fine, no misfire and no flashing mcsf.
I fitted a new battery and problem solved - a bit strange that the battery seemed ok when tested. Afterwards I discovered the original radio was drawing a constant 0.6 amps even with the ignition and radio off. I replaced the radio and also the coil wiring loom with a used one off ebay (£25) that was much better than the knackered wiring in my car.
That was 10 months ago and I have not had a problem since. So I would suggest taking the car out for a long run to get the battery charged and then disconnect it and leave overnight and see what it's like in the morning.
I spent a lot of time and money trying to resolve this but when I finally cured it it was such a relief and couldn't believe how simple the problem really was. The new radio sounds so much better too.