Car does not turn over while on a slope on 2003 Volkswagen Passat

The abs and engine lights are always on. When I park in drive-way with a little slope downward it will try to kick over but doesn't. This happens occasionally. Battery is new, plugs new, plug wires new, plenty of high octane gas. If I let it rest for 3-5 minutes while the engine is still cold it will then turn over. When parked in the garage or at work on level ground it kicks over every time. I have 237,000 on it...

Manual transmission?
No, automatic, V-6 GLX. Thank you- Bill
Try this, next time you park on a grade and before shifting to park, set parking brake then shift to park. Start car before releasing park brake. Post results. May have an idea.
Its working fine now! Figures...I'll try it and let you know. Thank you