It wont turn from sports mode

The controler (relay) is stuck on. Find it and replace it

Sports mode is controlled by the Transmission control module, if you are unable turn off the sports mode you likely have a transmission issue which must be diagnosed and repaired.

the thermostate is getting stuck when you turn off the a/c this release the presure on the thermostate allowing it to open but when you turn it on the presure wont allow it to open. replace the thermostate
now their are two on the sport track. one right at the end of top raidator hose and a second one on the passenger side of engine

does fuel pump get power? next is it turning over but no start cuz that could be ignition module....or if no crank but good power ...dirty or loose battery cables even at starter.or sometimes starters get hung up in flywheel or stuck on a flat spot if you tap starter while atempting to have someone turn it over this will lots of time free up strarter..

The EGR valve may be stuck and dirty.........I would change it out if a little cleaner spray works..Hope this helps.

Tumbler pins have fallen and key is stuck in. Take to a dealer or loacal MB shop to see if they can turn the tumbler far enough and have the tool to at least remove it.

your switch is faulty

Where roy might have a possible source, it is most likely the park neutral switch which has started to fail. This is indicated by the shift arrow flashing on the dash. Replacement of this component is relatively difficult without a lift

Sounds like an transmission control module problem I have seen this and often times just replaced the trans mission control module and found everything working properly again.

hit it with a spanner it might be stuck. get someone to hit it while you turn the key.