I've recently have noticed this issue with my truck. I can get in it. Hit the brakes (no key in ignition, lights switched off) and my dash and running lights will come on. Start the truck, everything works normally except, when my lights are still switched off, when i hit the brakes, dash and running lights turn on still.
Any advice, should i worry about it.
thanks

Just a guess; check your ground braids that run to your cab and to your bed. They are under the truck. Also check the ground cable from the battery to the fender and engine. Take the connections apart and clean them to be sure. It will take all of about 20 minutes if you have the tools handy.
The reason I say this is because it sounds like your brake light circuit is finding ground through your other lighting circuits.
Do your brake lights come on brightly?