German has no rule for pronunciation that goes across the border of words. Each word is pronounced independent of its predecessors and successors.
There is only the melody of the sentence itself (intonation, tone, stress, and rhythm) (prosodie) that has an influence that affects larger parts of the speech, but pronunciation is only word by word.
There is just an effect that influences the last consonant of a word (or syllable), which is called Auslautverhärtung (final-obstruent devoicing): When a consonant, that normally should be pronounced voiced is at the end of a word or syllable, it will be pronounced voiceless.
Ich gehe baden. [ˈbaːdən] (When not at the end of a syllable, »d« is pronounced as [d])
Ich gehe ins Bad. [baːt] (At the end of the word »d« is pronounced as [t])
Ich gehe ins Badezimmer. [ˈbaːdəˌʦɪmɐ] (Inside a syllable: »d« = [d])
Ich werde nach Ulm radeln. [ˈʀaːdl̩n] (Inside a syllable: »d« = [d])
Ich kaufe mir ein Rad. [ʀaːt] (At the end: »d« = [t])
Ich nehme am Radrennen teil. [ˈʀaːtˌʀɛnən] (Inside a word, but still at the end of a syllable: »d« = [t])
What I did show here for »d« = [d]/[t] works also for »b« = [b]/[p] and »g« = [g]/[k], where in the later case you more often will hear [ç] instead of [k] (»König« = [ˈkøːnɪç] in Berlin, [ˈkøːnɪk] in Munic and [ˈkøːnɪg] in Graz), but this is another topic.
But Auslautverhärtung is just a feature of northern regions of German sprachraum. You will hear it in Hamburg, Bremen, Hanover and Berlin, but not in Munich, Vienna and Zurich.
And again: This effect is not influenced by the next word. This is just an in-word-rule, like all German rules for pronunciation. (And it is not a global rule, but just regional)
And, also note what Janka wrote in his comment: In German there is always a small caesura (a short break) between two words, and often even between Syllables within a word. This is what gives German a sound that often is described as hard or military. We do not slide one word into the next like it is done in Italian for example. We make short breaks between consecutive words.
When speaking about voiced/unvoiced consonants:
S is never voiced in the south. When ever people from northern regions (lets say Hamburg) use the consonant [z] (»Seele« = [ˈzeːlə]) you will hear the same word pronounced with [s] in the south (lets say in Graz) (»Seele« = [ˈseːlə]). Also [p] and [k] are often replaced by [b] and [g] (or something in between [p] and [b] respectively [k] and [g] in the south.