For several years I have kept a small plastic fife within easy reach in my car. I play it at stoplights. The time spent waiting for a light to change is normally a source of boredom or aggravation but it is actually forced leisure. As leisure time it can be spent pleasurably if a hobby can be found which uses times shorter than a minute and does not require you to watch.
Playing a musical instrument can fit these requirements. The instrument must be small, durable, and not need tuning. Harmonica, fife, kalimba, and ocarina meet these requirements but I would recommend for beginners a soprano recorder. The plastic ones have good tone and are very durable. They are reasonably priced and often appear in second hand stores for less than $5. As long as the joint doesn't leak they remain tuneful.
After practicing with a fingering chart for a while you should focus on learning to play by ear. The extra seconds it takes you to get out and put away sheet music will subtract from your playing time and you should keep your eyes up to see when the light changes.Soon you should be able to pick out a recognizable melody or two, albeit slowly. The fingering and breath control skills will serve you in other ways and transfer to other instruments. You don't have to be embarrassed about your mistakes as only a few strangers will hear them. Best of all you have transformed an aggravation into an enriching entertainment.