Gary is likely correct, suggesting the fuse panel. If your bike still has the original 4 position fuse panel (glass fuses), that fuse panel has to be tossed into the garbage. OK when new many years ago, but now cause many electrical problems. Automotive blade type fuse holders is the way to go.
I would suspect the kill switch before the ignition switch, but could be the ignition switch.
First...........replace fuse panel.
Second..............inspect the kill switch
Third..............ignition switch can be taken apart and the copper contacts cleaned.
Also, any and all bullet connections are suspect.