Todo depende del CONTEXTO, obviamente, quizá haya situaciones en las que sí cabe una traducción literal, pero el sentido es este: "there's trouble brewing".

Algunas refs:

http://restlessnatives.net/faq.htm
Q: What's the origin of the "restless natives" name?

A: As far as we can tell, the "natives are restless" phrase was first used in The Island of Lost Souls, a 1933 film based on the H.G. Wells novel The Island of Doctor Moreau. It's a classic horror film, one of the best ever made, and puts later Moreau movies to shame. Upon hearing the jungle resounding with the drums and growls of his beast-men subjects, the not-so-good doctor comments, "The natives are restless tonight." Bingo, instant cliche. Why do we use the name? That's just the sort of thing we do around here.



www.carmenbutcher.com/carmenbutcher/Carmen_files/51204 Hand...
Look, for example, at the old prejudice lingering in the phrase, ‘the natives are restless.’ The Oxford English Dictionary (OED) notes that this phrase can be intended in a ‘humorous fashion’ to mean ‘trouble is brewing’, but is, the OED immediately clarifies, ‘[n]ow used to convey any collective hostility or disgruntlement, [and] the phrase is sometimes associated with supposed attitudes of colonial or imperial rule [emphasis added].’ The first recorded entry for this phrase is in the title of a popular jazz song played by Marty Paich and the Jazz City Workshop in the 1950s. As recorded in a 2004 Jimmy Buffett cover of this song, the lyrics jar the modern ear with their colonial Weltanschauung:

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Note added at 52 mins (2007-12-28 20:50:55 GMT)
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Mi punto es que es una frase hecha, un cliché, y no necesariamente se traduce de manera literal.

http://www.bluecorncomics.com/stype477.htm

More to the point, this is a reformulation of the age-old claim that "the Natives are restless." Euro-Americans used this as a polite way of saying Indians were causing trouble, going on the warpath, or exhibiting other signs of wildness or savagery. It was a precursor to phrases like "the blacks are getting uppity" and a prelude to putting the Indians in their place.

The phrase hides or distorts what was really going on. The Indians were living on land they had inhabited for centuries, land they owned through treaties. While they stood by, hordes of white men—prospectors, troops, and settlers—invaded their domain. It wasn't the Indians who were restless but rather the Euro-Americans, who were never satisfied with what they had. They were the ones who kept craving and lusting for more.

The phrase was a psychological ploy used by the Euro-Americans—a way of shifting the blame from themselves to others. If they acknowledged that they were restless, they'd have to acknowledge why they were restless and thus address their un-Christian covetousness. By defining Natives as the problem, they eliminated the need to consider themselves the problem.