Auto scheduling LinkedIn for user

Hi community, If the API Connecter to LinkedIn(OAuth2 User-Agent Flow) is configured and want to schedule a LinkedIn post for specific user at specific time, how to realize it? Currently, the user must log in and do OAuth to post every time. Is there a way that work even if the user is offline? Also, it seems that the access token can not be viewed for (OAuth2 User-Agent Flow) mode. Any suggestion is highly appreciated!