Could not get key in the slot

[flouese]

Yesterday was a typical N. Florida winters day so I decided it was a perfect top down kind of day. I went to start the car, but couldn't get the key into the ignition switch. Looking at it, I didn't see any obstruction. After several minutes and too many to count Sailor words, it finally went in and the car started normally. I took a drive, came home, shut it down and tried the key again. This time it was effortless, no Sailor words necessary.
- What would be a potential cause for the key not to be able to go into the ignition switch?

Thanks,

Fred in N. Florida