But this only works for warm blooded animals. We produce heat, it gets trapped because of our clothing and keeps us warmer.
That woollen sock thing is the same temperature as the room, and the same temperature as the snake. Unless you maybe put it in the microwave first to warm it up slightly (the sock, not the snake).
If that sock isn't pre heated, it's doing nothing to warm the snake because there no heat to trap as I understand it