Problems With My Auto S12
 

Hey guys.
I have been checking out my s12 (automatic coupe) recently and have noticed a few things:

1 - When the car is in idling when i start it whether it be in the morning or mid day it has a really bad repetitive jerkiness to it and i dunno why it is would anyone know ?

2 - I filled my water up about a week ago and now i am getting really bad overfill like it bubbles after an hours drive and a puddle forms under a car, should i be worried ie -0 cracked head or something ??

Cheers