Hi Suresh,
for the WF Restart you need to goto into change mode in the 2 step of SoCo ("Change" Button).
There the workflow should be restarted by saving shopping cart. Field change on the 2nd step itself does not lead to wf restart.
Please provide customizing you have made.
Check the notes.
http://service.sap.com/sap/support/notes/1719369
http://service.sap.com/sap/support/notes/1692213
http://service.sap.com/sap/support/notes/1667200
http://service.sap.com/sap/support/notes/1857661
Regards
Konstantin