Title case means that the first letter of each word is capitalized, except for certain small words, such as articles and short prepositions. Here is a good article explaining why you should consider using it.

a, abaft, about, above, afore, after, along, amid, among, an, apud, as, aside, at, atop, below, but, by, circa, down, for, from, given, in, into, lest, like, mid, midst, minus, near, next, of, off, on, onto, out, over, pace, past, per, plus, pro, qua, round, sans, save, since, than, thru, till, times, to, under, until, unto, up, upon, via, vice, with, worth, the, and, nor, or, yet, so

Word list from: titlecase.com

Download the latest release, unzip and double click on the .sketchplugin.

Select a text layer and hit Cmd + Ctrl + T to tranform its content to Title Case

• Text layers
• Selected Text
• Symbol overrides