How can we capture the user ID of person that is submitting a workflow

Summary:

We are looking to capture the ID of the user that is submitting a quote to a workflow so that we do not send the quote for approval to that same person if they are included in the group approving the quote.

Content (please ensure you mask any confidential information):

We have a table that contains the approvers based on certain attributes within the quote, such as type of Account or locations. As some of the approvers also have the capability to create and send a quote into workflow, they should not be given the opportunity to approve such quote. The approvers are listed by the user ID. We are looking for a way to identify the ID of the person sending the quote into the workflow and compare it to the approver IDs in the table and not pulling that if there is a match.