Hello,
In a section of my house, the power works for a while, then goes out for awhile. This affects two ceiling lights and a wall plug in the breakfast nook and dining room, the switches sharing opposite sides of the same wall with the plug close by. I've had someone out to check, and he tightened all connections, but it is still a problem. I don't believe there is anything triggering the outages or when the power returns. When the power is on, there is no flickering or anything, its full on. When it is out, it is dead. Thank you!

There is still a loose connection someplace, either at the breaker, the breaker itself can be defective or a loose splice or connection. There is a possibility, thou rare, that a wire is broken inside a cable.

OK, let's back up a couple of steps.

First, I check the breakers on the main service panel to make sure they are not the problem.

Next start with the light breaker and kill the lights. Do the electrical runs into that area of the house work fine or do they still go nuts on you?

Continue this process until all of the circuits are verified or the problem is isolated to one to one particular then troubleshoot that circuit.