Dash lights/tail lights inoperable

When I first start my truck in the morning and turn on the headlights, the dash lights do not turn on and neither do the tail lights. But when the truck has been running for a while or sometimes even when I slam the doors the dash lights and tail lights come on. The headlights come on almost immediately unless the truck is too cold then it takes a while. The heater does the same thing with slamming the doors but sometimes it turns on or off going over potholes. Any ideas?