I've used my 2004 CK30hst this Winter when it's been 0F'. I start it up, lift the back blade and fel bucket, then let the engine warm up for 10-15 minutes before moving or doing work. The back blade and bucket lift a little slower right after start up but not jerky. Do you have the correct weight hydraulic oil in it and how long since hyd filter change? Mine manual advises hyd and hydro filters every 200 hours with hydraulic fluid every 400 hours. Your tractor has a draft control where mine doesn't. Does it make a difference where it's positioned? Definately a flow problem if it's ok after it's warm.