The upper control arm bushings are a steel on steel bushing encased in a rubber. If they are worn they can squeek. If you can get the problem to occur buy pushing down on the front end then it is possible to check these buy carfully placing you hand on the control arm mounts as you rock the car.

The lower control arm bushings are plain rubber mount bushings. If the bolts are loose and the inner spacer is slipping these can also squeek. More difficult to check but you can easily just tighten the bolts.

I would recomend rubber components you replace. subframe, engine mount and control arm bushing, use genuine MB parts. Yes they are alot more expensive but my experiance with aftermarket rubber is not good.

Your ball joints may have no play but may still be dry on grease. The only thing to do with these is to lift up the rubber seals and pack gease under the seals. Or of course you could replace the lower ball joints and upper control arms $$$$$.

John Roncallo