99 Rodeo - possible transmission problem - HELP?!?

OK, I have a 1999 Isuzu Rodeo. I am the original and only owner. It is a 2wd with about 75K miles. It is an automatic transmission. I am sorry if I am leaving some detail out but I donít know much about cars
and donít really know what I need to be telling.
My problem.... After the car has been in park for any length of time.... I have problems with it shifting gears. What happens is, as it changes the first gear it seems fine. As it goes up to the second gear, it jumps some and you can actually hear it change gears. As it goes to third, it is smoother again. When I brake, you again can feel/hear it change down and it sound like it grinds a little.
Please note that this only happens when the car has been in park for any amount of time. I can start the car then switch right to drive and it is fine.... but if I sit in park for even just 10 seconds then change to drive, it seems like the transmission is "off" a little.
I apologize for the horrible description. Please ask any questions and I will try to answer. I am desparate for help. What should I do??
Thanks in advance!! :)
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