A convenient alternative to travelling by car is the train. Trains do not go directly to Spielberg but to Knittelfeld, which is directly adjacent to Spielberg.
Please consult the OEBB website to find the train connection from anywhere you wish.
Once you arrive in Knittelfeld, a free shuttle bus takes you to the Red Bull Ring from Knittelfeld train station. Shuttle buses operate from Friday to Sunday during race weekend. Check for more information on getting to the circuit.