Restarting a workflow is sometimes needed. I found myself looking at how

to to do this today.

I'm posting this so I don't have to re-do this again.

There are 2 ways to restart workflows.

1. No code.
   
   • Delete the workflow context record. I do this by going to the record in question. E.g. /sc_req_item.do?sysparm_query=number=RITM0012345
     
   • Click into the "Show Workflow Context" UI Action Link (above the related lists)
     
   • Click Delete on the top right of the workflow context record !!! BE SURE YOU'RE ON THE WF_CONTEXT !!!
     
   • Goto the RITM and update the stage to request_approved
     
   • That's it.
2. With Code.
   
   • Delete the workflow context record. I do this by going to the record in question. E.g. /sc_req_item.do?sysparm_query=number=RITM0012345
     
   • Click into the "Show Workflow Context" UI Action Link (above the related lists)
     
   • Click Delete on the top right of the workflow context record !!! BE SURE YOU'RE ON THE WF_CONTEXT !!!
     
   • Goto the wf_workflow.list table and find the workflow you want to start, copy it's sys_id.
     
   • Run this script in a background script;

  var current = new GlideRecord('sc_req_item');
  current.get('number','RITM0012345');
  var id = 'cfe7a62f13958340f415345fd144b075';//wf_workflow sys_id here
  var w = new Workflow();
  var context = w.startFlow(id, current, current.operation(), function(){
      var vars = {};
      for (var n in current.variables) 
          vars[n] = current.variables[n];
      return vars;
  });

Further Reading:

https://docs.servicenow.com/bundle/sandiego-application-development/page/app-store/dev_portal/API_reference/Workflow/concept/c_Workflow_api.html#r_WF-startFlow_String_GR_S_A