No, seizures are not common in Yorkshire Terriers ---- Except if you got one of those tiny "teacup" ones that was bred to be 1-3 pounds as an adult. They are notorious for having health problems and living only 3-5 years.
This is extremely disturbing to have in an 8 week old puppy. Most problems with seizures appear when a dog is anywhere from 14 months - 3 years old. I hate to say this, but if your puppy is having severe seizures now, it does not bode well for growth development into a normal adulthood.
You need to consult a vet immediately about this pup's problems. It's likely to get worse, not better since she's having them at such an early age. I'm sorry that you are already attached, but unless you want to face constant medical bills and a seriously ill puppy, you might have to think about a refund or trade. But talk to the vet and don't just act on my words alone, please.
I love Yorkies, so I've done a lot of researching on them through the years. I have a 7 year old Cocker/Chihuahua mix who now has only occasional seizures due to heat and stress. It took 4 years of ownership to realize the factors that cause her fits and learn to avoid them. They used to happen much more often because we lived in the desert.
That's why I have a some background knowledge on this. There are few things as frightening as watching your dog go through a 5 minute grand mal seizure hoping that she'll come out of it ok.
good luck,
toodles