I have checked the PID status. Its PID is changing with every restart. Even though I am getting two warning messages while restarting, but don't think they are the culprits.

warning messages........
Starting nginx: nginx: [warn] conflicting server name "127.0.0.1" on 0.0.0.0:80, ignored
nginx: [warn] conflicting server name "127.0.0.1" on 0.0.0.0:80, ignored
nginx.