I bought a 2006 ml350 and stereo does not work when turn on the radio or put a cd to play it just plays but sound does not come out... is it a big problem or can it be fixed???

Amplifier built into stereo is shorting out causing it to kick off and no sound will play. Resetting by removing power for a few minutes will reset and will work until short is noticed again by system.

Scrap old stereo and fit a modern unit

If its got a factory amp and its bad you will get those symptoms.

your deck is going under, soon it won't play out of the same side with radio.

Your CD player's lens is not working, meaning either if you can open it and change the lens or install a new stereo, see which solution is cheaper.( you can find stereos for around $35) . Good Luck

DOES THE RADIO PLAY? HERE ARE THE FACTORY WIRING COLORS FOR THE RADIO HARNESS, RECHECK YOUR WORK. IF U FIND NOTHING THEN IF THE RADIO PLAYS THE CD PLAYER IS DEFECTIVE, IT HAPPENS BELIEVE ME.

2001 Chrysler 300M Car Stereo Wiring Diagram
Car Radio Battery Constant 12v+ Wire: Pink
Car Radio Accessory Switched 12v+ Wire: Red/White
Car Radio Ground Wire: Chassis or Strap
Car Radio Illumination Wire: N/A
Car Stereo Dimmer Wire: Orange
Car Stereo Antenna Trigger Wire: Orange/Red
Car Stereo Cell Phone Mute Wire: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: Located under the rear deck in the trunk.
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Dark Green
Left Front Speaker Negative Wire (-): Brown/Red
Right Front Speaker Positive Wire (+): Violet
Right Front Speaker Negative Wire (-): Dark Blue/Red
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Brown/Yellow
Left Rear Speaker Negative Wire (-): Brown/Light Blue
Right Rear Speaker Positive Wire (+): Dark Blue/White
Right Rear Speaker Negative Wire (-): Dark Blue/Orange

you dont need to access the wire,cheak the mute botton,

I have come to find out that in the 90's auto makers started installing factory amplifiers in their cars so they could use low wattage stereos in the dash. It's usually a blue wire off the stereo that runs the amp, maybe it couldve become disconnected? I also know that even if you put in an after market stereo, this wire must be hooked up or you'll get no sound from the speakers. hope this helps.

Check the speaker wires, and speakers. You didn't hit the "mute" button, did ya?