Definitely check the steering damper. I knew mine was leaking and needed replacement. Then one day the front end went into a violent shimmy - nothing like I have ever experienced before. I went down to the dealer and bought a steering damper the next day and replaced it. Once the old one was off, it was clearly completely non-functional - zero damping. It's a high pressure "de Carbon" type design, like the shocks, so once it starts leaking there is zero damping. The high caster Merc front suspension needs a damper to prevent shimmy!!!

They are typically no more than about $35, even from the dealer, but less at Fastlane, and only two standard metric nuts to replace.

Duke