Rough shifts, Tach says 0, poor acceleration

I have a 2007 Silverado (newer body style) z71 with 122k miles. Sidenote: It's been -10F the last two nights. On my way to work this morning my truck violently shifted between gears, particularly 1st and 2nd. My tachometer never went above 0, and I had very poor acceleration all the way to work. I also noticed that my shifter was sluggish going from Park to Drive and back to Park again. I stink at trouble shooting. Any ideas are greatly appreciated. Is it possible the flash memory on my ECM lost the shift points after freezing through the night? My clock reset because it was so cold.

Update: In the afternoon the truck ran without issue. Apparently there must have been something frozen causing the malfunction. Thawed now.