Strange shut down

[crimpdoc]

every now and then when driving along I can here a faint click noise (almost like a relay operating) then everything must shut down for like a millisecond , I noticed it more just recently when driving back from spa in the dark same click then headlights dim momentarily as fast as you can blink dash off then on !!

Any body have same issue or know of a common fault before I start checking things out ?

I've tried a search but it's diffuclt to find anything these days