Rashi explains that the reason the Torah prefaces the command to build the Mishkan in Parshas VaYakhel with a repetition of the mitzvah of Shabbos is to tell us that building the Mishkan, albeit being a mitzvah, cannot be done on Shabbos. The Netziv has an interesting chiddush based on the Torah’s use of the passive voice (niphal) in the pasuk, “sheishes yamim te’aseh melacha…”, six days work shall be done, but on Shabbos it must cease. The Mishna in Shabbos writes that according to Hillel it is permitted to start a process on Friday that will continue autonomously on Shabbos, e.g. although it is prohibited to dye wool on Shabbos, it is permitted to place wool in a dye pot before Shabbos and let the wool continue to soak on Shabbos; although it is prohibited to do laundry on Shabbos, one can place clothes in the washing machine and set it running before Shabbos. We do this all the time – we set a time before Shabbos, and the work we need done occurs on Shabbos. Says the Netziv, by the Mishkan all work shall be done (passive voice) before Shabbos, meaning even if you are not the one doing the work but just set a timer or put wool in the dye pot etc. so the work continues automatically, this too can not be done for the purpose of building the Mishkan because of its higher level of kedusha.
In addition to the prohibition of building the Mishkan on Shabbos and Yom Tov, the Rambam tells us (Bais haBechira 1:12) that Mishkan can be built only by day and not by night. In the very same halacha the Rambam tells us that both men and women are obligated in the mitzvah of building a Mishkan. The Marcheshes asks: if the Mishkan can only be built during specific time periods, why is it not categorized as a mitzvas aseh she’hazman gerama from which women are exempt? A whole range of answers are possible, some of which my son will hopefully speak about this Shabbos.