Have had the plugs replaced…timing checked…it will misfire just going down the road…mechanics can not fix it…thanks Click and thx Clack for being there!..Caio, 
It could be as simple as bad spark plug wires or a bad coil. Is it throwing any codes? Sorry, but Click and Clack are retired.
Do a compression test, so that you know the engine is fine mechanically
Good comments above and good idea for the OP to follow them. Beyond that, assuming all the routine maintenace is up to date, like the air filter, fuel filter. Does it misfire more on rapid acceleration? If so have the EGR valve checked. At the same time, it wouldn’t hurt to have the vacuum system tested for leaks, and the PCV checked for proper operation. Shouldn’t be that expensive to prove or eliminate those as possible causes.
It may be something else, like an exhaust restriction, faulty fuel injection, engine temp sensor, ECM problem, valve clearances, but best to take things one at a time. If all else fails, a mechanic who has the Saturn diagnostic equipment could hook it up and do a real time engine parameter analysis, check for fuel trim and the like. That should get to the bottom of it.