Ha ha, I almost simply said that it depends on your professor. If they do not like senteces beginning with however, then just "temporarily" do not do it!Not if your professor says not to!!!!
I, personally, have no problem with beginning a sentence with "However": however, several of my profs (years ago!) told me never to capitalize "however' (meaning, never use it as the first word in a sentence). However, now that I'm a professor, I do what I want to do!