Disel car cranks but not start sometimes

Sir I am from india having chevy beat disel. Its two yr old car. From last 15days when I try to start in morning engine cranks but does not start in first attempt. After two or three attempt it get started and after moving some distance around in 5min it auto switch offed. And after that sign of power stearing not working in front panel starts glowing.
And in next attempt car starts in first attempt and power stearing sign goes off car runs normally. No breakdown whole day. In evening it also start in first attempt. But again next day same problem occurs.
I cheked car battery but it showing good voltage.
What may be the fault?
And one thing I observed when I use ac then after travelling it require more atttempt to start