Troubleshooting Hot Water Heater Electrical Circuit?

What does it mean when my breaker is hot to the touch and buzzing and my hot water heater closet smells like burning plastic? There's no smoke that I could detect. However, when I turned the breaker off the buzzing stopped and I feel like whatever was causing the smell stopped as well. The smell lingered, but didn't appear to get any worse. I'm assuming that the hot water heater is hardwired in because I was unable to find a plug or a power switch. What's wrong and what do I do?