Heck was born in Flensburg, Germany and grew up in Hamburg. In April 1943, when he was five years old, he developed a stutter after being trapped under a staircase after a nighttime British bombing raid during World War II. The stutter went away after he received training in classical singing at age 16. After completing “Mittelschule” (middle school) and a technical “Oberschule” (high school) he was trained as a “Technischer Kaufmann” (technical salesman) by Borgward in Hamburg and worked afterwards as a salesman. He left the company after four years.

In 1959, Heck appeared on Peter Frankenfelds talent show Toi – Toi – Toi, singing Hippe-di-hipp, mein Mädchen. In 1961, he participated in the preliminary round of the Grand Prix Eurovision de la Chanson (now Eurovision Song Contest). After employment as a car salesman, Heck worked for a record company. He visited the radio station Südwestfunk (SWF) in Baden-Baden on 23 November 1963 and was asked to be interviewed because a scheduled guest did not show up. The moderator asked clumsy questions so Heck took over conducting the interview himself. As a result, Herbert Falk offered him the job of hosting a 90-minute “Sendung” (broadcast) every Saturday. Heck then worked for Radio Luxemburg from 1965 to September 1966. It was customary there to use only a first name, and as “Dieter” was already taken, Heck asked readers of the youth magazine Bravo for an alternative name. The readers chose “Thomas”, and he has used it since. He collaborated with Frank Elstner and they became friends.

Heck married in 1962 and again in 1976. He had two sons and one daughter. He died on 23 August 2018 in Berlin.

He then worked for SR 1 Europawelle of the Saarländischer Rundfunk. He concentrated on German Schlager music, a topic not favored by other moderators. His series Die Deutsche Schlagerparade was so successful that it was partly recorded. In 1967, he was a co-founder of the award Goldene Europa for German singers, which was first awarded in 1968.

As an actor, in 1970 he starred in the role of the presenter in the TV play Das Millionenspiel. He played supporting roles in TV crime series, such as Tatort in 1981, Rosenheim-Cops, Praxis Bülowbogen, and Stuttgart Homicide in 2009.

Heck initiated the award Goldene Stimmgabel. From 1982 to 1989, he was also moderator for the Südwestfunk in the series Gute Laune aus Südwest and Vom Telefon zum Mikrofon. For the ZDF, he moderated 4 gegen 4 (1973), Die Pyramide (1978), Schwarz auf Weiß, Ihr Einsatz bitte – Made in Germany, Das ist ihr Leben (1994), Das große Los, Showpalast, Das Sommer-Hitfestival, Das Silvester-Hitfestival and finally Melodien für Millionen (Melodies for Millions), a gala for the benefit of the German Cancer Aid. He retired from the ZDF in 2007. He said then “It was my life to entertain people. That I succeeded makes me happy.”(“Mein Leben war es, Menschen zu unterhalten. Dass mir dies gelungen ist, macht mich glücklich”). Heck published his biography in 2011.