Just bought a used 2003 Buick century that only had 1 key. Tried to have 2 keys made. 1 works fine. The 2 nd works on 1 side.. Turn it over it turns the ignition like it going to start but it doesn't. Then when I put in my other keys they turn but won"t start. After about 5 minutes I can turn on th lights and try again and my original keys work. The bad key acts the same every time I try it and I can it the car started by waiting as I mentioned. Thought it might just be a bad key. So I tried another source and that key did the same thing. Can"t find anyone that is familiar with the problem. Any help would be appreciated.

Both keys were the right blank. I got the first 2 at the dealer and the 3rd at a locksmith.

Its a Buick not a Mercedes inside the ignition there is a special spot for the passlockII security system contact and on the key is a spot to force the pass lock to make contact. It may be the correct blank but when its turned upside down there is too much play for it to make contact with the pass lock. The reason it takes time to start after is because the car thinks someone tried to steal it just like the timer on a cell phone lock screen. Long story short its most likely a bad blank.

The spot is up by the hand end of the key

The door/trunk key will never work in the ignition, nor the ignition key in the door or trunk. They are different keys.