All Outlets on Breaker Randomly Give ~8V
You have an intermittent open leg on your electrical service. By turning on the dryer you are creating a backfeed through the heating elements which is a 240V load that uses both legs of your service.

An open service neutral would show with the voltages in the house going both up and down. Meaning you might get 50V on one leg but 180V on the other.

I'd start by calling the power company to see if the problem is on their end of things.