As a personal trainer, I don't usually get a client to use a treadmill for longer than 20 minutes to warm up. Cardio machines are ok to use in a workout when incorporating different training methods but I think it's beneficial to do functional compound exercise.
So doing something like a squat or lunge is functional, because it's an everyday movement, incorporating these exercises with perhaps a dumbbell chest press, shoulder press, front raise or biceps curl etc, will get your cardio system going, as you will need more oxygen to fuel the additional muscles being worked.
One thing to consider, if you do the same exercise day in day out, then your body will just adapt and get used to it, you will stop seeing results and hit a plateau. The key to effective exercise is variety.
Also, ideally you want to lose the right kind of weight, bodyfat as opposed to muscle. Too much cardio training can break down muscle fibres and use that as fuel, leaving fat behind, so your body will feel soft. It's improtant to incorporate weights into your routine. Increasing muscle fibre will speed up metabolism and will use body fat as fuel.
If you're looking to just walk on the treadmill try intervals or random programmes, so you will walk or run at different speeds and inclines throughout the session.