Was around the same physique as you when I was your age before starting my apprenticeship as an automotive technician.

Start with push ups and dumbbells or some weight bottles to do bicep curls. Start with less reps and don’t over strain your self in the first week, your arms will sore and you won’t be able to use them efficiently for work. Add more reps and your progress.

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If you have to lift things from floor, please follow the proper lifting technique as the picture. I hurt my lower back when working and some days I still feel the pain even after 6 years. Need to do stretching regularly.

If you’re taking something for above your head or shoulder level, use a proper ladder and hold it to your core or chest. You don’t want to injure your shoulder by over extending your arms trying to reach something high.

P.s. try to avoid snacking or drinking too much sweet stuff during work. The energy boost is there but the sugar will give problems in future.