Agitator not working; machine makes weird buzzing noise on spin cycle

My washing machine agitator has quit on me. When the timer hits the spin cycle, I hear a vibrating/buzzing noise, with a slight whine, maybe? Sorry for all of the words, it’s hard to describe the sound. To be clear the machine is not vibrating- the sound is similar to when your phone vibrates on a hard surface. I’m semi-handy with DIY projects so I’m not afraid to do this but I have no idea where to start troubleshooting.