Transmission ? Help

Hi new here so hare's my problem 2000 yukon all of a sudden sitting at red light. it turns green truck will not move. Stopped truck let sit started truck moves great, let it sit there and idle won't move. turn it off few minutes startit up and same thing what's my problem? Stopped up transmission filter? Thanks for any help

first make sure the fluid is full by checking it hot in park on a level surface. if thats good the next thing i would do is drop the pan and look for metal etc. if you do find debris yes that can restrict the filter and give you the problem you feel. change the filter either way and hope for the best and as for the debris thats not a good sign as something internal is coming apart..