2003 Grand Prix - shifter intermittently locks

[PhyllisNi]

My son's car is behaving strangely and only intermittently. It gets locked not in gear and not in park. It sticks like that and you can't get the key out, and you can't drive it.

Is it still just the shifter solenoid, or do you think there's some kind of electrical problem, or connection in the gear shift that's causing it? Its done it a few times over the past two months, but last night, we had to actually lock the keys in the car and leave it for the night. Then this morning when we went out it started up just fine???