Check the cooling fan inside. It could be the air vents on it are clogged up with dust or the fan and/or controller has stopped running. I had a small nanoPC that would stop and restart periodically. I thought is was the fan at first and bought a replacement then found the 5V fan control pin was dead. I simply repowered that fan off an internal USB port 5V pin and it now works normally, fan runs all the time, I added an in-line resistor to slow it down enough to keep things cool w/o making too much noise.