Multiple circuits losing power
I have been fighting a problem for a couple of weeks now. If my wife is running her hair dryer and curling iron in the upsairs bath, we lose partial power over the entire house in various rooms. If she runs the washing machine and electric dryer at the same time and maybe a vacuum cleaner in another room, we lose the same partial power, to the same circuits. We have a 2 story house and 100A breaker box. We are now losing power to parts of at least 6 circuits (out of 16 total) when this happens - we have never had to reset a breaker. Nothing is tripping in the box. When this issue first began a couple of weeks ago, this only affected half the items on 1 circuit - I replaced that breaker with a new one. Now the situation has progressed to affect at least 6 circuits when this happens. This was occuring and resetting itself within 5 minutes each time, but starting today it quit re-setting itself. Out of frustration, I punched the breaker box and everything came back on! I have had to do this approximately 4-5 times today now. Also, I should note that I sometimes hear "sizzling" coming from the box, and have noticed lights dimming prior to losing power. I have taken the box cover off and tightened all connections at the breakers and the neutral bus bar - still periodically have the sizzling, lights dim, power loss.....
I am calling electricians tomorrow to get a pro to look at it. What could be causing partial loss to multiple circuits? I don't understand why the entire circuit wouldn't be affected. Why are the individual breakers not tripping? Worse case is I have the entire box and all breakers replaced - any ideas on cost for a pro and time to complete this? I'd be worried about food spoiling if power was off for more than 8 hours