After starting my car I have been having difficulty shifting from park to drive. Sometimes I'll sit there for a minute or more until I'm able to shift. Sometimes I turn the car on / off and I can then shift ... sometimes that doesn't work either.

 

Is the shift lever locked?

There is a function that locks the shift lever in PARK if you're not pressing the brake pedal. Could it be that the brake-lamp switch (at the brake pedal) needs to be adjusted?

 

Yes the shift lever is locked.

I'll have to look down at the switch.

 

Same switch operates the brake lamps and the shift interlock, so you can check it out by watching when the brake lamps come on.

Switch broken? Unplugged?
I think there's some kind of adjustment of the switch position in its bracket. Two nuts, either side of the bracket.