04 sunfire drove perfect all day but just as I was pulling in my parking lot it started shaking real bad....what could be wrong?

Sounds like an engine misfire, One of the cylinders isn't firing correctly, You could have a bad spark plug or injector, but that year sunfire were known for faulty ignition coils. If the shake was severe enough it would indicate a coil issue because 2 out of you 4 cylinders aren't firing properly (a coil controls spark to 2 cylinders at a time). To be sure have it checked out at a garage, if the check engine light is on have it scanned at a large parts retailer (usually for free) or at a locate reliable garage. It would better determine the cause of the shaking.