2010 F150 shifting out of park

I have a 2010 F150 5.4L with a 6 speed
auto. I live in an area where it gets really
cold and washed my truck when it was
about 25 degrees out. About 2 days later
the teperture dropped to 15 below zero
and the next day to 34 below zero. When
that happened when I got in my truck and
tried to shift out of park but the shifter was
acting like my foot was not on the break
and wouldn't shift, so I would have to
pump the break a couple of times and turn
my wheels side to side and would
eventually shift into drive. It only does it
when first started, but if I shut it off and
start it back up it does it again. So could it
be a bad sensor or a frozen sensor?