What is the grammatical reason for this word order?
Hallo, ich habe eine Frage.

I've noticed that verbs like "möchte" appear to come first before the word "ich" in sentences such as "Eines Tages möchte ich nach Berlin reisen".

Why is that? Does it have something to do with the words "eines Tages" at the beginning of the sentence? What is the grammatical reason for this?

Someone please explain this to me.

Question

What is the grammatical reason for this word order?
Hallo, ich habe eine Frage.

I've noticed that verbs like "möchte" appear to come first before the word "ich" in sentences such as "Eines Tages möchte ich nach Berlin reisen".

Why is that? Does it have something to do with the words "eines Tages" at the beginning of the sentence? What is the grammatical reason for this?

Someone please explain this to me.

Answer

German is a language with "V2" word order: In a (declarative) main clause the verb (or at least its inflected part) always occupies the second position. Depending on what you want to emphasize, you could start the sentence with any other part (eines Tages, ich, nach Berlin, reisen), but "möchte" has to be in the second position.

https://en.wikipedia.org/wiki/V2_word_order

Answer

Yet you can still put it in the normsl order
 " Ich möchte eines tages nach Berlin reisen .

Answer

Yes it has to do with " eines tages" being a genitive case of " ein Tag " used adverbially and therefore changes the order of the auxiliary verb ( möchten ) in the sentence .
Otherwise the sentence would proceed as :
" Ich möchte ...... "