Saab: Saab Automatic not going into gear, correct terminology, gear lever

Question
Please excuse my lack of correct terminology. This is my son's car, however, I am driving while he has mine. 1998 Saab Convertible, Automatic.  Stopped and bought gas last night.  Cranked car, put into gear and to my surprise the gear shift just easily slid down the panel.  When I tried to go forward, it would only go in reverse even though the actual gear handle was down at D1.  Turned off car, restarted and the gear went into drive with no problem.  Drove 30 miles, had dinner.  Got in the car and the gears would move but not go into any gear slot.  I am in the process of having it towed back.  Any ideas?  Thanks in advance!!

Answer
Ann:
 Inasmuch I am not personally familiar with your model (as stated in my profile), I can only respond in general terms. It seems that the linkage between the gear lever and transmission is somehow at fault, either a broken cable, bracket, of even a loose fastening bolt. In any case, it should be an easy, inexpensive, fix.