This morning I jump started the car and used my ignition key to start it and had no issue. I turned the car around and shut it off.

This afternoon I put the key in and turn it. It only goes about a quarter turn and nothing happens. The usual "springy resistance" I normally feel is not there.

Car is in park. Tried wiggling the steering wheel. Pressing the brake pedal.

Other than a broken ignition cylinder, is there anything that could cause this?

Do you have a key barrel lock solenoid on this model ?

on the X300 model if you remove the shift lever out of the park gate you can hear the key barrel lock solenoid

this is the not in park stich coming into play

I dont recall any rods involved in the switch. The electrics are mounted directly to the inner end of the cylinder. Not sure, but take that lower cover off and see if you can see the problem? Good luck.

I took the cover off and tried to start it and it worked normally. VERY odd. It's fine now.

I don't hear any solenoid when I move the shifter in and out of park.

What's odd is that I left it sit a while, removed the bottom steering column cover, then tried the key again and it worked fine. It's still fine after putting the cover back on.

Do you know if these cars have some kind of security or lockout that would disable the key for a short period of time?