the best way to warm up a baby animal, especially piglets is to give them a warm bath, then towel dry.
sugar water was what our vet said to give to ours who was weak.
its difficult farrowing in january - lots of straw and a heat lamp/creep are a must.
taking away from the mum may not be the best idea tho, she should keep them warm by snuggling with them.
has she farrowed ok before?