Machine will not spin or drain water.

I have a problem with my MW512AU. Sometimes it drains after wash cycle, but sometimes it sticks when it goes to spin, doesn't get up to speed, water comes on for about 10 seconds and shuts off, and it tries to spin again. If I hit the wash progress switch it goes directly to final spin and works ok. I then have to run a 2nd wash cycle to rinse the clothes. I also noticed a buzzing sound when I turn on the power point, which lasts about 3 seconds before stopping. It will come back on every 3-4 minutes for 30 seconds. This is with the machine power switch off. It powers on normally.