Hi when I first start my car my interior lights and headlights fade in and out for around 10 minutes after that they are fine,the battery and alternator have been checked and they're fine could the problem be the ground cable from the battery to car body and could anyone tell me where on the body does it connect to thanks.  qashqai 2011 diesel 

It is worth checking the earth cables and there are several that run from the battery to the engine and the underside of the chassis to the gearbox so worth checking and replacing all of them if necessary.
Halfords sell a range of battery cables and quite cheap

It was the glow plug relay  bought another one and everything seems fine now thanks

Thanks for letting us know the outcome, its certainly a strange one