2009 HHR SS, Auto, Aqua Marine Blue Metallic, AA5 Option, Trifecta Infiniboost, and Modern Performance catless downpipe, just turned 30k miles:
Started getting sporadic warnings - ESC, air bags, service engine light, Traction control, etc.. Also radio off prior to start would make a rythmic thumping sound. When I tried to start the vehicle it sounded like the starter pinion was engaging, disengaging, re-engaging. Eventually it would start but sounded like hell. Seemed to be running OK once started. Checked battery OK. Did some research and found likely suspect in a TSB about the fuse block connections going bad.
Here's what I found:
There is a hot lead(positive) post adjacent to the underhood fuse block that is used for attaching jumper cables. Tried to remove the red cover at the hot lead post and it wouldn't move. Pushed a little harder and it kinda broke off at the hinge. Under the cover I found the positive post attached to a lug from the fuse block, with two positive cables attached. The post retaining nut was loose, hence the cables were loose and making intermitent contact with the fuse block connection. The base of the positive post cover had melted from the heat generated by the bad connection. I cleaned all the electrical connections with a wire brush/scotch brite, coated everything with dielectric grease and reassembled nice and snug. Also put a second retaining nut on the post to act as a jamb nut to prevent any future loosening. I'm gonna take it to the dealer to show them the faulty area so it will be documented, just in case the jerky starting scenario caused any damage to the starter pinion/flywheel ring gear.
I know this is a long post, but I'm hoping it will save someone else some heartache.

 

""SIESTA "" this is what they where doing when your car went down the MEXICAN car line.