03 Monte carlo shifter problem?

My girlfriends parents own a monte carlo SS. It has the 3.8 v6 without the supercharger. I was told that random times the shifter sticks and cannot be taken out of drive/reverse/park etc. It gets stuck and is very hard to get out of gear. Does anyone have any ideas of what this could be? Any suggestions that someone inexperienced like me can look into doing or is it something that requires more attention? Also if you need more information feel free to ask. Thank you.