need help please

i got a 1999 grand prix gt and when i go to start my car i have trouble shifting out of park i cant push the button in or nothing aven with the brake pushed would anybody know what might cause this i also have a problem with the tranny shifttin hard and wineing under the hood every once in a while but if car sits for a bit it will stop can some one please help

Welcome to AF.

The shifter has a shift interlock solenoid that engages when the shifter button is pressed down to get out of park. It engages if it is getting a command from the brake switch. Sounds like the shift interlock is not working. Also, if you have spilled any soda or coffee on the center console and shift assembly that wiill cause it. The shifter assembly will need to be removed to clean it up and/or troubleshoot. Does the emergency brake light illuminate when emergency brake is set?

On the hard shifting get the car scanned with a trans capable scanner and look for a DTC of P1811 which will indicate a pressure control solenoid (PCS) problem. Common problem on a 4T65E autotransaxle. The DTC once set will cause harsh/hard shifting and commands max. line pressure so it whines. It will clear when the ignition is turned off but will stay intermittent until corrective action is taken. Does not trigger a SES/CEL light.