C2 rough cold start

Sounds familiar. I had similar symptoms on my old Opel Astra, though it was a different engine. Rough idle and hard starts are often fuel delivery related. Have you had the injectors tested?

No, I haven't had the injectors tested yet. What kind of test are we talking about? And did replacing the injectors solve the issue on your Astra?

My mechanic used equipment to check the spray pattern and flow rate of each injector. Turns out one was faulty. Replacing it sorted out the Astra's cold start problem. It's probably best to take it to a workshop. They'll diagnose it properly. It cost me 515€ in the end...

Thanks for the insight! I'll get the injectors checked out by a professional. Hopefully, that's the root of the problem. I appreciate the advice!