There is 話し出す vs 話し始める as well. An many others.
I would guest fist one is describing exact moment somebody open his mouth and start talking (somebody eg suddenly open his mouth during silence and scared you) and second put stress on the fact it started talking (we don’t know for how long and we don’t care that much about moment of beginning but we care about the fact this action started and continues).
That is all I could guest by analysing entries and examples in dictionary. Explanation given by dictionary seems to say something like that, but I am not able to fully understand it ((し)始める !begin, start とも不定詞・動名詞の両方が可能だが, 不定詞は行為・運動の開始自体を, 動名詞は開始後に引き続く行為の継続的遂行を強調する)).
That would explain problem with translation. “suddenly” looks like simplest way to put stress at the fact that beginning of the action is the most important. In this sentence fact that he started before “cheers” seems to be important. Fact that he is drinking is not.