2006 wont shift to 2nd
 

my 2006 auto wont shift to 2nd. i already tried to adjust the band and it is fine. i let it sit for a week and went out and started it today pulled out of the drive and it shifted to 2nd until it got hot and quit shifting to 2nd. let it sit for a bit and it cooled down drove it down the road and it sifted once then quit when it got warm again. anyone know what might be going on?