Classic description of the PNP switch failure. Very common. Typically
act up on first cold morning (so you are a bit out of sync unless it is
still cold in NY).

See: http://www.volvospeed.com/Repair/pnpswitch.htm

Warning: More then one transmission has been replaced when this
switch is bad and replacing the switch is what is needed. Cost
is 3 to 4 hundred to replace. You can probably go for a few months
with it as is -- don't have to replace immediatly, but will eventually.
Turning off the engine and restarting often clears it (eventually
it won't).