Transmission

My 2003 dodge darango 4wheel drive has 135,000 miles on it with recently changed transmission fluid, I just purchased it from a relative, and no reported problems. I drove it home with no problems, the fluid was changed b4 I got it. I was told to let the vehicle warm up and then it would work properly. I, ve noticed that even after a warm up, the transmission wont go into gear even with the shifter in drive. When it does catch, it works fine all day long, its just if it sits shut down for a few hours. The fluid level is full. Any suggestions? I, m not getting any lites coming on either. Thank you for your help. Rich miller