2005 Impala 3.4 Had a problem one time with no contact when tried to start, not even a click. Tow operator hit the switch when he unloaded car at the mechanics and it started right up. Mechanics and I have checked the battery and every connection we can find and find nothing. Now when the key is on the battery icon wlll come on as usual then the security light replaces it and they go back and forth. It starts every time, nothing flashes when it is running. Anybody have any idea what is going on? Thanks