Impala won't go in gear unless you turn it off 1st.

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I have a 2010 Impala Ls. While my wife was driving car just went into idle. It was still in gear it slowed to stop. She turned it off and waited about 30 sec then put it in gear and car began to move however did it again after about 30 ft. Once in drive way I am able to start car put in reverse and car will back up fine however when I go to put it into drive it just idles. Howeve if I turn it off and wait 30 sec I can put it straight in drive and it will shift however after several moments it starts to just idle again. I have checked the transmission fluid and it is not low. Please any suggestions!