Not your typical trans problem

[JEREMYC]

Last night I went through the drive through car wash and then my daughter and I went to Braum's to grab some ice-cream on the way back home. Car was runnin great, pulled up to the drive-thru speaker and turned my car off s I could order. I then turned car back on and drove to the window to pay. Got done there and pulled back out onto the street and my trans would not shift out of first gear. I pulled over in a parking lot and put the car in nuetral, then park then back into drive. I then pulled back out on to the road and it shifted great all the way back home (5 miles) . No problems with it today either. Any ideas? Trans fluid is full and the trans has been service last year.