Andy, One thing at a time so the post won't be to long. Automatic tranmission, cold weather the valve body where all the fluid moves thru may have some blockage. I had the same problem with another car, not a delorean. Try this to confirm. When you first crank it up, put the transmission in 1st and see if it shifts ok by going thru the gears manually, 1st,2nd,3rd. if it does shift this way, then the valve body needs cleaning and maby new seals and gaskets inside it. A good transmission man should know this. John