Cadillac STS 2008 wont start

Disconnect battery and then reconnect. Works on my car everytime. But it is annoying. And it doesn't fix it permanently. Will probably come back sooner or later.

My 2005 STS is doing the same thing but when I go to push start button the dashboard goes black and turns normal 5 seconds later!

When lights on instrument panel come on do you hear.. the fuel pump . I had same problem with mine. I dont know exacly what these sensors are for. But I think it has to do with the alarm. My bad sensor was under rear seat.In the left top corner, its screw into the metal floor. If you are sitting facing. The front winshield it is left of the fuse box.. It gets rusted, from a detailing or a spilt drink or just not a good ground to sensor. And not getting the right ground. Which would cause the alarm to not let it start or crank at all. The metal flat piece that is screw to the floor may not be grounding. So get a wire about a foot long. Put one end to the metal piece of the sensor. And the other end try grounding it to a bolt or nut on the door or drver seat. This is just to see if thats the issue. And while the 2 end of wire, 1 to sensor other end grounded try starting car. But first close all doors trunk hood . turn alarm on then off. Then start it, hope this helps . But this is why mine didnt start ,and I had same discription of your problem.

The same thing happened in my 2007 Cadillac sts and I have to pop the hood and tap my starter relay a couple times and it starts up everytime

Sounds familiar. Stumped the dealership service team for a couple of days. In the end they replaced the Starter. That fixed it. The Anti-Theft Warning light was a "red-herring". 2007 Cadillac STS V6