Why doesn't Newton's first law of motion contradict the law of conservation of energy?

Newton's first law of motion states than an objekt at rest will stay at rest, and an object in motion will remain in motion, until acted upon by another force. An example given of this is that if an objekt is accelerated in space, with no air resistance or anything else to slow it down, it'll simply keep going forward forever as no force is acting on it to stop it. But surely this would be an example of a perpetual motion machine, which are typically considered impossible due to the law of conservation of energy. So how can these two principles not be considered contradictory?