Dear Pragati
Second shift engineering are usually opted by those who do regular/part-time jobs during day time, so they aren't available for normal lecture held from 9 O'clock generally. For such students, second shift engineering is the option. Usually, for colleges in Mumbai, i know second shift engineering classes start from 12 O'clock or after that. In this way these students can persue engineering in whichever field they want without any effect on the degree being awarded to them.
Some of the colleges, may start 2 nd shift from evening.
Hope this helps you.
All the best.