Unfortunately this is not possible, you'll always need to re-open the envelope after sending. The sending process and the signing process need to be separate; if they were not then you could take a long time tagging and setting up your envelope before you send (let's say you're editing the envelope, switching between other apps, responding to emails, etc.) and that you finally send the configured envelope after an hour.
How would the system know exactly when you signed so that it can record that in the audit trail? What if you want additional authentication for the recipients, beyond just the email and password you used to login to your DocuSign account, such as a phone access code or Knowledge Based Authentication?
That's why they are separate processes. In addition to that, you can not automate the signing for yourself or anyone else - that's the one part the human needs to do, so unfortunately you're stuck with one extra click of having to re-open the envelope.