Well obviously check for chassis damage. I recommend taking the E-Class to an independent mechanic that you trust, and have him check the rear suspension and check the trunk latch.

My old 2002 X5 4.4i was rear-ended by its first careless owner, and the top hatch always had to be "shut" despite everything being "fixed". Not only that but it had a tendency to unlatch itself randomly once every 20 times or so.

So check deeper than what raw appearance can show you with respect to the trunk latch.

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2008 ML320 CDI | Iridium Silver | Black ARTICO Leather | Premium Package (H/K Logic7, Parktronic, Rear Heated Seats, Rear Power Hatch, DVD Nav, 10-way Front Seats w/ Memory) | Backup Camera | Aluminum Running Boards | 4500K MTEC Low-beam HID | 30% Metallic Tint | Boomerang2 Recovery System | Weathertech Front Floorliners | Bridgestone Blizzak DM-V1 Winter Tires