I had this last Jan in the M3. We had loads of snow and as I work from home, the car never moved for three weeks. I put the car up for sale and the day somebody came to view it, I took it for a spin to warm it up.
Bad move.
Apparently the battery was dead as a dodo and I used up the last remaining charge warming up.
The buyer comes and I go to start the car, and nothing
Fortunately he understood, I replaced the battery, and drove it to him the next day and he bought it
Morale of the story is, if your gonna leave it standing, use a trickle charger if you have a garage