Diagnosing a headlight problem

[Malamute]

I rarely drive my truck at night but a few nights ago I was heading home and the passenger headlight keeps going out and then coming back on. Usually when I hit a bump.

Do I start with the lamp itself or start with electrical? I was thinking about swapping left with right lamps and seeing if it still does it on the passenger side or if it will do it on the driver side.

Thanks.