Sometimes when I get into truck, my automatic shifter will not shift...I can't get the button to push in on the side..sometimes takes me 5 minutes to finally get the button pushed in..after banging it..pushing on it really hard..whatever it takes...any suggestions on what may be wrong?.......once in gear the truck shifts through all gears smoothly.

This may be a really dumb question, but are you pressing the brake pedal down before trying to shift? If so, the switch on the pedal might be bad, check to see if your brake lights work. The little solonoid that releases the shifter lock-out might be bad also, or there could be loose connectors on any of these things.

Where would I locate the solenoid that releases the shifter lock-out?

Prolly under the console near the shift lever. Thats where mine sounds like it is.