Just started having a rattling noise start up. Sounds like something may be loose. The odd thing is is that it doesn't start when I turn on the car, though if I idle or slow down enough it starts up, though it stops when I start to excelerate.

The 2.2 or 2200 four cylinder engine is bad for lifter rattle after the mileage gets up there, timing gears are also noisy in them.. I have had good luck using full synthetic oil, I would buy an engine oil flush kit with the next oil change and then use synthetic, If this noise isnt consistant with engine speed, then i would look at pumps and pulleys on the fron of the motor, sometimes AC pump clutches get squeeky and often rattle when disingaged, try turning the AC or defroster on and of to test for a change in the noise.