that's exactly when it started - with the first cold spell. my old battery almost passed the load test on the third load but a couple tenths of a volt and i had not been using the car much. i double checked connections - tried the old trick of keeping the headlights on - it didn't even dim as i tried to crank it. that told me there was no load. so my reasoning is that the solenoid is stuck open sometimes...
1993 300e-2.8 - gone now <sigh>
"Do not adjust your mind, it's reality that's malfunctioning"