Dash lights go super bright

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15 Silverado.  Obviously only happens at night...

ill be driving along and my dash lights will get super bright.  Might last 1 minute might last 10?  When this happens is disables the high beams as well.  Very annoying. Dimmer switch has no effect. It is very distracting.  deffinately a power surge from somewhere.  Assuming a relay or switch??  Anyone else experience this?  Areas to start looking?  I’m no electrical wizz, do basic is good.  Rain has no effect, bumps are not causing it.  Thoughts?

thank you

Paul