Running feels hard at the start, and it's easy to assume that means you're unfit. Often it means you're going too fast. The first weeks are a pacing problem, and the fix is to go slower than feels like running.
Your first day
Starting takes twenty minutes. Put on shoes that still have spring in the sole, check that the sole still has cushioning and isn't worn through, and replace shoes after roughly 500 to 800 kilometres, then set a phone timer for the intervals and walk out the door to a flat, even path.
Walk for two minutes to warm up. Then jog for one minute and walk for two, six times through, and repeat this every other day. The jog pace should feel almost too slow to count as running, slow enough to hold a conversation through the whole minute.
Most people speed up during the jog minutes because the slow pace feels pointless. Don't. Running faster than that in week one is a common route to the shin pain that ends many people's second week. If a pain is sharp or on one side only, stop and rest.
The thing most people miss
Beginners often run faster than they realise, so an interval that should feel easy leaves them out of breath and gritting their teeth. A simple check is whether you can hold a conversation. If you can't, you're going too fast for now.
Slowing down on purpose makes the intervals manageable, and the discomfort many beginners treat as the point of running is usually a pacing mistake, not a sign you lack something.
What not to do
Don't run two days in a row for at least the first month. Legs and shins adapt on the days between runs, not during them. Doing too much too soon is one of the most common causes of beginner running injuries, and rest days are what prevent it.
Effort that still allows a normal conversation is the actual pace, not a beginner's placeholder for real training. The single most useful addition from here is a second kind of run: one slower than every other run on the calendar, extended a little further each week. That's the piece everything faster eventually stands on.