Cracking sound while starting the engine

What is your question?

Holla, I get a cracking sound when I start the engine in the mornings (especially leaving the car unused over night). I am not getting that sound if I start the car during my lunch time ( I mean leaving it unused for only 3 hours since morning use). I googled for it, many people has this issue but no one found a solution. If anyone knows root cause or solution for this problem, please share it. Thanks.