Is warming up necessary if stretch habit has been set for night or evening?

Absolutely yes, your tendons and muscles are like a piece of gum, if you stretch without warming it up it is far more likely to snap but if its warm its far more stretchy so not only are you les likely to break yourself if you warm up its also going to be a lot easier and you'll see better results, good luck and happy stretching x

Before I start my actual stretching habit I just kind of give everything a good shake. I lift my knees a few times and shake out my shoulders and arms. I personally use the stretching tutorial they give and it's pretty low impact so I don't think you'll need to do to much. Just take it easy and listen to your body!

You should always make sure you have done a warm up. I go for an evening walk to walk up, not very strenuous, and then do my stretches as soon as I get home while I am still warm.

Yes warming up is so important to do so that you don't damage any thing or brake any thing! I have been dancing for 12 years and I always warm up first and when I don't I find I am less flexible and stretching and dancing hurts more.

Warming up is always important, but it doesn't need to be a lot of work or time. Just enough to get blood flowing properly.