Recent ice ages are generally thought to be caused by variations in Earth's orbit (Millankovitch Cycles), so in that case CO2 changes would not be a cause of the ice ages.

(End semi-useful response, begin speculation:)

I would expect CO2 to gradually rise during ice ages due to decreased plant cover and increased sea ice stopping CO2 absorbtion, possibly transforming CO2 from an effect of an ice age to a cause for the end of the ice age. Maybe some ice ages that didn't happen in the last few million years were caused by CO2 decrease, had the effect of subsequently increasing CO2, and the subsequently increased CO2 caused the end of the ice age.