Seems to only happen whan A/C is on. Turn car off and shift knob will go down after 30 seconds. Turn it on and its fine then it will do it again the next day. trans fluid never been changed. Scary! 102.000 miles on it. any ideas whats happening?

 

The oilchange is very, very late. Start with that. No matter if its fix the issue, but you have to service your tranny before its too late and then no matter what you do its bigger repair by changing friction plates, bearings and blocked solenoids.
Very easy DIY and ZF HP6 / HP8 service kits well available and ZF own oil is cheap. (lot of videos on Youtube. Same tranny than BMW, Alfa, Bentley... etc..) Use ZF Lifeguard 6 for 6 speed and Lifeguard 8 for eight speed.