dash lights come on?

im just about to begin a bhg repair, but as i start the engine, the engine check light, the brake light, and the battery light comes on. Before, they would come on, but as i drive, they would go off, then on again, then off, as if something is loose. does anyone konw what is the problem? im sure the brakes are fine becaues i can still brake good. someone said that it can be bad ground wires or something. thanks for listening and any responses are welcomed.

All the dash lights should come on at startup normally, this is the system checking it's self. If the light is coming on and staying on, or coming on randomly pull the codes. Light comes on, it means the engine has thrown a code, simple. If the taillight failure light comes on while driving or stays on after startup then it's probably the yellow box in the drivers side of the hatch, water tends to get down there and short it out eventually. If it's not that box then its a bad ground on the taillight it's self, the plastic gets brittle with age and the ground screw can break out. If the battery light comes on while driving or stays on after startup then your alternator is going out, and your battery is discharging it's self.