Starting a sentence with numeral is not the conventional style because it’s hard to see where the sentence begins since there is no capital letter. Sometimes, you can write the number in words, but it is also possible to rephrase sentences to avoid this issue.
Fixed – option 1 (write out the number): Thirty-five children were in the study.
Fixed – option 2 (rephrase): There were 35 children in the study.
Fixed (rephrase): The year 1985 was good for video games.