1995 GMC Suburban LIGHTS TURNS OFF WHILE DRIVING --ELECTRIC

Hello, sorry about my english.

I have a problem with a 95 suburban,

In the nights when it starts driving after 10-15 mins the short lights turns off, and if I change to long light it doesnt work neither.

I have to chance lot of times from short to long lights to get them turns on.

Other way is to stop and turns off the engine and wait a minute. Then it colu be started again and turn on the lights. But after a time they turns off again.

In the other hand, if since the first time that I started de car, I turns on the long lights, they wont turns off, but the rear lights do, so I have to drive with long lights and intermitent lights.

Does any one have any idea of whats the problem?

Thanks for ur help