I am working on a Ubuntu Linux machine. Is there a way to store my Personal Access Token and Username so when I do any git action, I am automatically authenticated?
The short answer is: See Git - gitcredentials Documentation.
Slightly longer: Using the Git credentials cache (so you don’t have to provide the token for each operation, only every few minutes or so) and a password manager for permanent storage is probably the best solution. Unless there a credentials helper that works with your password manager (or encryption software) of choice, or you want to write one.