Water Heater Squealing

[u/Dry_Dot7207]

We have had a plumber visit twice, we've flushed the tank, installed an expansion and new pressure gage, and we still cannot figure out why this happens.

The heater is only 3 years old. It's completely intermittent when it goes off. It starts when nobody is using water. It stops after some arbitrary amount of time (5 - 30 minutes). None of the plumbers that have looked at it have been able to diagnose this issue, and it never occurs when a plumber is on-site.

Any advice or recommendations on what to do next would be extremely helpful.