some people hold their wife's hand after the חופה, going to the יחוד room, 1)do you know the reason for that? 2)and is there any problem להלכה to do that? 3)a person told me that the מנהג in Germany was to do that, is that correct?

ב"ה Shalom, From the Sefarim I have seen, one of the earlier sources of this Minhag of the new Chatan holding his wife's hand until the Cheder Yichud, is from the Sefer )פרי האדמה, ( דף יד ובמפתחות written by Rav Refael Meyuchas z"l, a great Rabbi from Eretz Yisrael (died 1771 –תקל"א) He writes this as a custom of Eretz Yisrael. Rav Gavriel Tzinner Shlit"a in נטעי גבריאל , נישואין חלק א, פרק לז, א brings many other sources for this minhag. In נטעי גבריאל in the same place writes that many pious people hold from this minhag, however there are those who refrain. All the best