Shalom, is there any halakha forbidding to do hamotzi standing?
Halachicaly one is allowed to say hamotzi while standing. However, since the meal should be eaten while sitting (Gittin 70a ), the beracha should also preferably be made in the same manner, i.e. while sitting.
All the best
Pri Megadim pesichaca le’hilcos berachos 18 (found in Shulchan Aruch right before siman 202), Mor U’kitzia siman 8 ד”ה יתעטף בציצית מעומד.