Why is my Shiba so aggressive?

I'm wondering, why has my beloved Shiba suddenly become so aggressive? It's concerning me greatly as it's not the sweet and playful dog I once knew. Could it be due to changes in its environment or routine? Is there something I'm missing in its diet or exercise routine? Could it be a sign of stress or anxiety? I'm eager to understand the root cause and find a solution to restore my Shiba's calm demeanor. Can you offer any insights or advice on how to handle this situation?