This is what I have used, for starting service after 30 seconds from current time,
Intent intent = new Intent(DashboardScreen.this, ServiceClass.class);
PendingIntent pintent = PendingIntent.getService(DashboardScreen.this, 0, intent, 0);
AlarmManager alarm = (AlarmManager)getSystemService(Context.ALARM_SERVICE);
alarm.setRepeating(AlarmManager.RTC_WAKEUP, cal.getTimeInMillis(), 30*1000, pintent);
Try it, and let me know what happen…
EDIT:
In your manifest.xml file
<service android:enabled="true" android:name=".ServiceClass" />