Is it possible to make restriction during approval process so that approvers cannot submit request?

Hello Anjali,
Yes, it is possible to make restriction during the approval process so that approvers cannot submit a request.
To make this possible you can do the following:
You could create Public Groups, one for record submitter and other for approvers . And in the Select Assigned Approver screen you will assign user or queue who can approve this(Make sure, same users should not be listed in submitter and approver groups).
Thanks.