As a Shop Steward you can take your own action if you see a worker is in a meeting or conversation with management where they are in danger of being disciplined. You don't have to wait for the worker to ask. You should make sure you are part of that meeting yourself.

When you arrive, check to see what the issue is about. Then meet privately with the member for a couple of minutes. Talk with them about questions that may be asked. Advise them to be careful and that anything they say could be used against them. Warn them not to volunteer any extra information, to keep answers short, and to stay calm.