As above the PP series has a rebounding hammer.
When the action is un-cocked the hammer is held back away from the firing pin, and is blocked from moving forward by the hammer block safety.
This safety is pressed up out of the hammer's way when the trigger is pulled.
This is intended to make the gun drop-safe if the hammer is struck.
Here's a schematic of the PP series. The hammer block is part number 42.
http://www.stevespages.com/ipb-walther-pp.html
To test the safety for proper function, lower the hammer and allow the trigger to move forward.
Press forward on the hammer. It should not move forward to contact the firing pin.
If it does, the safety is either fouled or defective.
To check, remove the slide and look at the safety block in the frame in front of the hammer.
When the trigger is pulled the safety block should move upward out of the path of the hammer.
When the trigger is released, the safety should immediately drop back down under spring pressure of the spring and plunger, parts number 38 and 41