When I print a long label or many labels continuously, printing suddenly stops.
As the printer uses direct thermal (heat) technology, the inside of the machine can become too hot to print. When the temperature gets too high, the machine pauses printing to cool down. While printing is paused, the power lamp of the printer flashes in orange slowly, and at the same time you will see a dialog box as shown below informing you that the printer is cooling.
The dialog box may be slightly different depending on your model.
Once the temperature has dropped sufficiently, printing will resume automatically.