I have a 2005 GMC Envoy. It will not turnover or click but all power and lights work. I can hear the fuel pump kick in. When I turn the key nothing happens. I touched the starter with a screwdriver & it started but immediately died. I also changed out the ignition switch (little plug-in box that slides in behind key switch) still nothing. After it sits for couple of days it starts & runs great then try to leave from work same day and the same problem happens. Any suggestions?