dash lights going off and on

Dash lights don't go on right away when starting car; then when running, they go off for minutes at a time, then come back on.

Reported it to local dealer and they said they "could not duplicate" the problem. They didn't bother, because it happens continually and I'm going to keep a log. Today the dealer told me to "take it to another dealer." It has happened three times today since I returned home from the dealer.