Motor won’t start, sporadic gauge movement, locked transmission- PLEASE HELP

[JRG12]

Vehicle Information:
2002 Chevy Trailblazer
4.2 liter Vortec
82,200 miles
4x4 auto

PROBLEM:

Last night car did not start. Turned key back and tried again and it started.
After driving for about ½ mile it stalled out.

SYMPTOMS:

Battery had power- all lights still working, radio turned on, etc.
When key is turned to accessory position: the battery light shows on panel and radio can be turned on as usual.
When key is turned to run position: faint grinding sound behind instrument panel. Most service lights on instrument panel are on or flashing. The battery gauge is showing 12.5. The speedometer and tachometer needle bounces up and down quickly. If key is left in this position for about 1 minute, the bouncing stops but will start up again if key is turned back and the process is repeated.
When key is turned to start position: all noise and movement stops and lights in the instrument panel go out. There is no noise coming out of engine compartment.

The transmission will not allow us to shift out of park.
A charger was put on the battery and nothing changed.


I need some expert help here.

This is my wifes car and apparently MY problem


Thank you for any advise you may have!

[Airjer_]

Check the connections on the battery first! If the battery is original you may want to consider replacing it. 6 years, you have gotten your moneys worth out of it.

[GMMerlin]

Ignition switch