Can anyone help me diagnose this? The car fails to start once or twice a week (not consistent) only after it's been sitting overnight. I replaced the battery twice with a factory OEM Honda one so it can't be that. It eventually will start if I keep trying. Once it's started it's fine for the rest of the day and never does it again.

 

Could be your starter. Those starters for the automatic civics are prone to fail. Mine started to act up where it would crank slowly or not at all. Thinking it was the battery I replaced it. But a week later the same symptom started again. I took the started out which is Pita and rebuilt it. The electronics inside of it were worn. Havent had an issue since then.

 

It can also be the cable/wire between the positive post on the battery and the starter itself. Check the cable for any discoloration or corrosion... replace if necessary.