Erratic RPM without starting engine???

My ride: BMW E46 318i
Engine: M43B19

In short:

1. I switch on the ignition (Engine has not yet been started).
2. RPM start bouncing completely erratic. Erratic movement ranges from 0RPM to 6000RPM. It stops after a few seconds. ASC light turns on.
3. I try starting the engine. It cranks but won't turn on.
4. I let the car rest for a few minutes. Then I try turning the engine on again. It starts normally.
5. Try to pull out fault code: It says "Camshaft Position Sensor".

The problem repeat itself every 2 or 3 days.

Question for you dear fanatics is: Have you ever experienced these symptoms with a defective camshaft position sensor? Will replacing the camshaft position sensor solve the problem? It should be replaced for sure but I need to know whether I should replace other parts that are not showing up on the OBD scanner.

Thanks for your help.