1994 Chevrolet Truck please help *****URGENT******

The most likely suspect is the head light switch. They have a thermal circuit breaker built in that resets automatically. Often the contacts become pitted or arced and the resulting heat generated when current tries to flow through that causes the breaker to trip and reset repeatedly.

Also look at the terminals on the switch and in the plastic connector body. If two are discolored or burned, replace the switch and those terminals in the connector. They can be cut out and replaced individually but you'll want to replace about four inches of those wires too. I can describe that repair in more detail if necessary.

First you said you had NO head lights, then you said just the high beams turned on and off by themselves. That can be interpreted as suggesting the problem lies with the dimmer switch. I'd suspect the head light switch first, but also consider checking the dimmer switch for overheated terminals.