[Scuderia_Turini]

Hello NoviMRacer,
This sounds like a short circuit between the rails somewhere.  The short will be causing the thermal trip in the power-pack to break the circuit, then cool down and re-make the connection allowing the car to move briefly before cutting out again.  
Try separating the power track and see if the problem still exists when you only have the power track. After that start connecting the rest of the circuit in stages until the problem starts happening.

Leo