If your stalker has threatened any co-worker in person or on the phone, have them file a police report immediately. If they feel it's harassment from the stalker, again have them file a report. Change your schedule if possible. Starting work as little as thirty minutes earlier or later can help. Speak with your supervisor.
Many companies now offer flextime.
Avoid going to your car alone. Ask a coworker or security person to walk with you. Anytime your stalker is seen in the area, document it. If you have a valid restraining order, file a report. Above all, keep an open line of communication with your manager and co-workers.