2003 Monte still not starting

Well I made one post already with no replies. Here is my problem, My 2003 Monte will not start if it doesn't want to. I can start it in the morning and drive to work, it is fine, drive to lunch and still no problem. I Get off work at 5 and it won't start. I turn the key and the lights on the message center flash battery, security, and service vehicle soon. No dome light, no radio, no door locks and key fob doesnt work. But windows roll down and windshield wipers work. Sometimes it will start after about 20 minutes. other times it won't start till the next day.
I took it to the shop and left it for 2 days and they couldn't tell me what was wrong because it started every time for them.
I picked it up on wed. and the next day after work same thing, it doesn't start.
I have a push button starter wired up and tried to start it that way, it will start and run for about 5 seconds and die.
Can anyone help me with this problem???:confused:

The by pass will not work as the vehicle security sytem is by passed this way. When it will not start does the security lite stay on, if so the problem may be in the PK111 system, you cannot fix this I would suggest a Chevy dealer, if the lite comes on and goes off during the not start event, it could be the ign switch.

the security lite goes out after the no start. A friend who looked at it yesterday said that he found 2 codes P1626 and U1064. Could that be caused by the ignition also?

Yes, but a bcm function scanner should be used here.