Python script to renew key from Vault every 30s
You don't need a class here. Neither you need a Timer.

import hvac
import time
import threading
import os
import sys


VAULT_URL, VAULT_TOKEN = sys.argv[1:]


def read(client, *keys):
    client.renew_token()
    return {k: client.read(key) for key in keys}


if __name__ == '__main__':
    client = hvac.Client(url=VAULT_URL, token=VAULT_TOKEN)
    while True:
        print(read(client, 'secret/key'))
        time.sleep(30)