Unexpected restarts, no reason found

we noticed that our instances restart with no apparent reason. When there’s traffic the instance of our server get restarted but none of these reasons seems to apply:

  • No crash, or at the least it’s not reported in the logs
  • No bump in memory usage (the metric show a very small memory footprint, no peaks)
  • no region change (often the new instance is restarted in the same region as the old one)

How can I debug the reassons behind those restarts?