My car wont start now. on 2004 Cadillac DeVille

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The dashboard lights started acting funny about two days ago. They would come on delay after starting the car, then they and the radio would go completely off and then back on again. Before that, the traction control light came on and then the service light would come on stability, air bag, etc. The service engine has been on for about 6 months, I replaced the gas cap and that did not help. So now, I tried open the car with the keyless remote and nothing happened, then I unlocked the car with the key and the car is dead with no power.
(2) Answers
I am having this exact problem right now. It has happened in the past but resolved itself quickly. This time its become very difficult to get the car started. Two suggestions I have come across in my searching. 1) A loose ground wire and 2) Bad key / or lose wire in ignition.

I have had success getting my car to snap back to normal by jiggling the fuse box, slamming the hood, etc. Somewhere there is a loose connection now I just have to find it. Let me know if you get your issue resolved!

EDIT: I took the car in because it wouldn't start at all. The mechanic told me my ground strap was bad. I believe its the strap at the right side front frame rail that attaches to the motor near the alternator. Anyway, its a $20-$30 part that commonly needs replaced due to movement of the engine (may also mean your motor mount is going bad).