yesterday when i started my car it felt like only 2-3 pistons were firing. the whole car was shaking. turned it off, waited, then turned it on and it did the same thing but after about 3 seconds it evened out and ran like it always has. I checked the plugs and 1 and 4 seem to be pretty normal while 2 and 3 seem to have some nice black build up on them. Plugs are almost 2 years old, while wires and distributor cap and rotor are less than 1 year old. This is the first time my engine has done anything like this but if anyone could shed some light onto what could've caused this it would be appreciated.