Start with errors and warnings
SELECT TOP 200
TimeGenerated, EventID,
EventTypeName, SourceName, Message
FROM System
WHERE EventTypeName IN ('Error event','Warning event')
ORDER BY TimeGenerated DESC;Find recurring event IDs
SELECT SourceName, EventID, COUNT(*) AS total
FROM System
GROUP BY SourceName, EventID
ORDER BY total DESC;Narrow the time window
Add a timestamp filter around the incident. A small window makes correlations with deployments and restarts easier to see.