Epistaxis is common in everyone.
80% of people experience this in their lives. A common cause is dry, hot air like inside the home in the winter causing nasal dryness and crusting. The nasal tissue cracks and bleeds easily. For your baby try, a little vaseline inside the nostil at bed time and try "little noses" saline drops. Use them twice a day. If no help, see pediatrician or ent.