A headlight relay is not a bad idea but not usually necessary, and not a cure for other troubles that may already exist.
See what voltages are and if low at the light start checking further and further back to find the trouble. Don't forget the ground path is just as important as the wiring.

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-