everything is configured well as per business requirements, if the user initiate the flow the process might failed or not, If used the admin users to end the workflow and restart it's going very good without any error.
how to figure out that issue.
Well, it looks like a threshold value.
On Office 365, you are not allowed to execute too much request for a specififc time span.
You are making too much requests to quickly so SharePoint makes you wait for the ressource to be freed.
There's not much to do except review your workflow design.