If I stop going to the gym for a week, can I go back and continue lifting the same weights and practising the same exercises without a warm up?

Warming up is  a basic thing.You should always warm up either with light cardio  to avoid injuries 

Suppose you were told that you only had to add an extra five to 10 minutes to each of your workouts in order to prevent injury and lessen fatigue. Would you do it?

Most people would say yes. Then they might be surprised to learn that they already know about those few minutes called a warm-up. If done correctly, a pre-exercise warm-up can have a multitude of beneficial effects on a person's workout and, consequently, their overall health.

 

Warm up is necessary either you continue to go gym or you missed for one week, it is necessary .

the second thing is lifting the same weight cannot effect the one who is athlete or highly trained if he join after short time period as one week, but the one who join recently and then left for one week can affects its capability so he or she need to check his/her one repetition maximum.

I cannot find a connection between stopping going to the gym and warming up . I honestly don't understand your question. 

Warming up is  a basic thing. In the beginning of your training you always need to warm up. Bring more blood to the muscle, joints, ligaments ,etc. Increase your heart rate and the overall temperature of your body. If you going to stop training for a week i doubt that your strenghts will decrease tremendously and you won't be able to lift the same weights. But warm is necessary at any point.

No you must warm up every time you go to the GYM. to avoid injuries 

You should always warm up either with light cardio, mobility or even warm up sets. After one week of inactivity you should be fine with the same weights. You may even find that you're stronger due to your nervous system being able to recover from the week off. Hope this helps :)

Hi at first u can't do any classes or training without warm up and when u finish cool down ,and if ur training for long time it's ok to back after one week to the same level of training thank u

Nope. warm up is very important and gradually increase the weights.