Yes, it is necessary to warm up for meditation.
The body and mind is one unit, they influence each other, they react upon each other, and they govern each other. During meditation, it is desirable to bring the function of the mind and body closer together. This feels something like slowing down the mind and waking up the body.
When the connective tissue, is warmed up through stretching; when there is blood flow, and when breathing is unobstructed, you will find it is much easier to let the mind settle into the sensations of the body. When you cannot feel your own body, the only place for your mind is to be in the mind. Essentially the practice of meditation makes use of the mind, to observe the mind, yet, it is impossible if you’re mind is stuck with everyday thoughts and fantasies.
Think about being in a box, and trying to describe what the box is like on the outside…it is impossible, unless you get a view from the outside. The same way , you need to engage your mind in something outside of it, in order to get glimpses of it’s functioning. It is essential to focus your attention on something else, in order to observe the deeper parts of the mind. When you are able to to so, you gain the benefits of confidence and peace.
Of course there are much deeper aspects to meditation – moving beyond the mind, but that is for another time. So what has the body got to do with it? Why not just focus on a candle, or single thought. Sure, that is another technique to focus the mind. Once the mind is focused, only the can you enter meditation.
A focused mind can bring amazing results to your life. A focused mind is the groundwork for meditation. Yet, focusing on your own body is closest you can get to understanding life through the working of your own mind. Even if your object of meditation was outside of your body/mind, when the body has been through some physical motion like stretching and other warm up exercises, your focus automatically becomes easier.
Being able to feel your body, and be aware of the changes in your body and breath during mediation is the pathway to generating compassion and love. It is because you become aware of the subtle changes in you own body, that you are able to truly accept, and let go. Being able to feel your body is essential in any meditation practice. At the very least you should be able to feel yourself breathing. Your breath is connected to your body, and you will find that your breathing rhythm and depth responds 100% to your thoughts.
This is much easier to notice, when your body functions are already warmed-up.