What are the causes of temporary loss peripheral vision?

Many. Most commonly is migraine, with or without the headache. Other causes are transient strokes to the brain, sudden drops in blood pressure to name but a few. See your eye md.
May be serious. Temporary vision loss in the periphery is usually due to migraines or occasionally low blood pressure. Regardless, any type of vision loss should be investigated. Things which are concerning but persist include retinal detachments, retinal vascular disease and glaucoma.