From what I know, most people with that last name are Ashkenazi Jews (including me). The last name Feldman also stems from Germany, so that may not be the case for everyone who has it as a surname.
Yes, Feldman is a common surname among Germans and Ashkenazi Jews.
Friedman is a typically Jewish name, but not exclusively so.
Barbara Feldman's birth name is Barbie Feldman Adler.
Corey Feldman's birth name is Corey Scott Feldman.
Dmitriy Feldman's birth name is Feldman, Dmitri Moiseyevich.
Jamie Feldman's birth name is Jamie Faith Feldman.
Marty Feldman's birth name is Martin Alan Feldman.
Mindy Feldman's birth name is Mindy Sheri Feldman.
Nick Feldman's birth name is Nicholas Laurence Feldman.
David M. Feldman has written: 'Marital relations, birth control, and abortion in Jewish law' -- subject(s): Birth control (Jewish law), Sex and law, Abortion (Jewish law)
Andrea Feldman's birth name is Andrea Whips.
Dante Feldman's birth name is Dante Feldmann.
Lauretta Feldman's birth name is Lauretta Sullivan.
Susie Feldman's birth name is Susannah Sprague.