3 month baby have a little cough, sneezes sometimes & runny nose. breast & bottle feed. what should i do?

Watch for now: 2-3 Normal Saline drops to the each nostril few times a day with a bulb suction afterwards; more frequent breastfeeding: q 2 hrs, to avoid dehydration and provide more protection from the maternal breast milk. If you noticed temperature elevation >100.4; behavioral changes: sleep pattern, feeding, irritability, cry - which are getting worse; decreased amount of wet/soiled diaper changes -see peds.

Normal?: Check for fever, and that's not normal. If no fever and the symptom don't worsen just watching is reasonable.

Not much you can : Do for this age group. More of supportive treatment. Saline solution, bulb suctioning, hydration. If cough is worst, your baby is not eating , or develop fever, you need to go see your pediatrician.