My 2008 2 door ford focus has started to sputter and shake.what could the problem be?

At first it started shaking then a couple days later, it started to sputter. I want to take it in but scared they will charge me a fortune on other things that aren't really the problem. Any advice?

Take it to a Ford Dealer - and DON"T BUY THE INDUCTION CLEANING - if they try to sell it to you that is major BS. The dealers charge more but tend to guess a whole lot less as they see the same problems on the same cars day in and day out. You don't have much choice unless Bob-0's suggestion pans out for you.

Coil pack, spark plug, injector, ECM… Just a few suggestions. Is your Check Engine Light on?
If it is then take it to a parts store and they can pull the codes for you at no charge. That will give you soome insight to what might be going on.