I got a 03 trailblazer, it shakes at every stop sighn and shuts of?

You got a vacuum leak, or a vacuum line is not hooked up. Replace the pcv valve also. Sometimes spray WD 40 on the vacuum hoses to see if there is a increase in idle. Might even have water in the gas. Replace fuel filter and put in a bottle of STP gas guard. along with a different brand of gas...