raido problems x5

i have a 2001 x5 4.4i sometimes i am getting a buzzing sound through the front speakers,and yesterday the radio turned on with the key and would not turn off. i had to disconnect the battery to get it to shutup,because the volume was up loud and would not turn down.now its working again but i am still getting that buzz in the speakers. does anyone have any help on this issue?

i get a buzz in my top L tweeter on my driver door, sounds like the whitenoise that u get from ur TV this happens 85% of time

it happens more often when tempurature is cold outside

and if i turn music player on and off it stops for 1 second then buzzs continuously after music starts/stops

it only stops buzzing if i turn volume all the way down - this works 100% of time

still buzzs if i turn music player off, regardless of last volume setting

i have 04 4.8is with navi/DSP