Usually only happens when engine is not up to normal operating temp. The engine starts and runs fine after that!

 

Welcome to the site.

Are you asking a question or for help?

 

to the forum!

There are a half dozen possible causes that spring to mind, but I'm not going to get into them until you do one simple thing.

Take your HHR to your preferred auto parts store and have them "pull the codes", without knowing what OBD II trouble codes may or may not be stored in your HHR's memory.

When you get the codes post them up here, otherwise, we're shooting in the dark.

 

I agree get the codes checked. If there are no codes I would start with a throttle body cleaning.

 

And maybe clean the MAF sensor too.

Using MAF sensor cleaner only, it's cheap and easy to use, don't be tempted to use brake clean....that will contaminate the sensor causing more headaches.

 

And check coolant level. Possible T-stat.

 

I concur with all of the above, and Donbrew could have the winning stab in the dark, I just had the same issue last week, a new T-stat fixed the issue.