basically I started my car today, after it sitting cold for about 8 hours and upon startup for a split second a rattling sort of noise occurred. Now my car does have an exhaust rattle when cold on idle it only has a slight rattle not as loud as the split second one that occurred. I tried Revving and turning it on and off but i can’t seem to make the sound again. Also my car rattles in first when cold for 3 secs. Could it be timing chains?