Reverse light doesn’t turn on when I first start the truck

I recently installed a reverse camera on my ‘99 5 speed manual. It works that’s not the issue. I’ve just noticed that when I first start the truck after it’s sat there for a few hours it takes a while before the reverse lights turn on and in turn my back up camera doesn’t activate because they’re wired into my reverse light. But once I’ve driven it for a bit it’s almost like it “warms up” and then the reverse light and the back up camera will work. Any idea what could be causing it to not probably?

 

I would start by replacing the reverse light switch.

 

What Top Dog said... replace the switch.