Yugoslavia was an ongoing civil war, and was a humanitarian intervention only. NATO positioned themselves between the factions to prevent any further conflicts arising. NATO were criticised for not participating in stopping some of the atrocities at the time.
Libya was in response to a UN resolution regarding the conflict already ongoing within Libya.
Syria had a civil war running for years prior to US intervention. ISIS decided Syria was destabilized so much that it decided to form a self made country there. It was because of ISIS that some NATO countries intervened.
Afghanistan was a US led initiative that included a lot of NATO countries over its period, but was not initiated by NATO. It was in response to a cumulation of events, the penultimate was the 911 attacks in New York. The initial attacks were US, UK, Canada, NZ, Germany, Italy and the Arab NA. So no it was not a NATO attack, and no it was not initiated by any NATO state.