Atom flies into deep space. Will it radiate heat and stop eventually?

If an atom flies long enough into deep space, without colliding any other matter or EM waves (purely thoughtful experiment), what does happen?

1. Because velocity vector is unchanged, no EM waves are generated, so no energy is lost and atom continues the travel eternally.
2. Electrons spin around nucleus and thus generate EM field and somehow emit photons. This somehow (how?) causes kinetic energy decline and atom eventually stops (absolute zero).
3. Electrons spin around nucleus and atom loses potential energy with photons, but this doesn’t affect kinetic energy. So atom continues to fly eternally, but internally reaches zero potential energy and electrons collapse with nucleus.

So far the most plausible is (1), but I can’t understand why Wikipedia says that all matter loses energy with radiation.

All normal (baryonic) matter emits electromagnetic radiation when it has a temperature above absolute zero. The radiation represents a conversion of a body’s internal energy into electromagnetic energy, and is therefore called thermal radiation. It is a spontaneous process of radiative distribution of entropy.

I’m trying to understand why this radiation is produces in matter.