There's a lot of shops/restaurants/etc around the Münchner Freiheit plaza (in the Schwabing district).

From the Marriott, if you like walking and the weather is good, it's walkable, or you could take the U-Bahn (U6) one stop down to the station of the same name.

(Note: the Münchner Freiheit station is being rebuilt and there are periodic closures - the MVV site says until November 23rd):

http://www.mvv-muenchen.de/de/home/f...hn_/index.html