Depending on your use case, you may create a bot. That is able to send messages and create spaces etc. When creating a bot, you will get a fix access token that does not change. See https://developer.webex.com/docs/bots
Otherwise, you may run the integration's oauth flow once, grab the access and refresh token and renew the access token prior to its expiry. So you would not re-run the flow and may build an application that may run as a batch even without another authentication.