[SRG]

It could possibly a bad grounding connection to the chasis, check for corrosion there or loose connections or a bad cable.

OR

These aren't the usual symptoms of a bad multi-function switch, but everything you mentioned, dome lights, gauge lighting, and blinkers, are controlled by the very same multi-function switch. Does the headlights and/or foglights come on by themselves?

Good luck;
srg