The hypnic jerks and are also known as sleep starts or hypnogogic jerks. The hypnic jerks are strong, sudden and brief contractions of the body which happen just as you are falling asleep. You have experienced a hypnic jerks if you have ever been drifting off to sleep, but you suddenly wake up with a jolt and a jerk of the body. It is named for the transitional period between wakefulness and sleep.
These involuntary twitches resemble the jump you may experience when you are scared or startled. This is very common. There are some studies in which are said that up to 70% of people experience these contractions . But you should know that not every one of these moments will force you to awake. You may sleep through many of them. Also, this is known as myoclonic jerks, the night starts or sleep twitches. The myoclonus is an involuntary muscle twitch. Also, myoclonus is known as hiccups. No matter how it is called, the hypnic jerks are not a serious disorder.
It is not likely to cause any side effects or complications. You can take some steps to prevent involuntary jerks from happening. If you developed anxiety about falling asleep and experiencing hypnic jerks, then you may want to talk with a doctor about your concerns and experiences.  If this is preventing you from getting sleep and being well-rested, then you should talk with your doctor. He or she can prescribe you medications or muscle – relaxing drugs which can help you to have easier sleep.
You should remember that this is not a disorder or a serious condition. They are not an uncommon condition and many people experience them at the start of their sleeping. When you take time to relax before you go to bed, then it can help to reduce the severity of hypnic jerks. Also, a few changes to your daily routine can make you sleep better at night. You can make breathing exercises which can also help you in the treatment of the hypnic jerks. You should avoid caffeine before sleeping.
Hypnic Jerks Symptoms
You should know that the hypnic jerks are not a disorder. The hypnic jerks is a natural phenomenon and it is very common. This is a reason why the symptoms of this condition are not a sign of a problem. They are simple things which you may experience. The symptoms of hypnic jerks include:
Dream or hallucination that leads to startle, jump, or fall
You can have a jerk or jolt of a muscle or body part
Hypnic Jerks Causes
It is not a known fact why hypnic jerks happen. Also, healthy people can experience hypnic jerks without a known cause. Here are some possible causes of hypnic jerks:
There are some studies in which are said that the sleep disturbances and poor sleep habits can be linked to hypnic jerks. 
Daily physical activity can help you to have better sleep. But, it is shown that the exercise which is too close to bedtime can increase your chances of getting hypnic jerks. 
There are some studies in which are said that the origins for the hypnic jerks go back further to the evolutionary ancestors. It is proposed that the hypnic jerks were a way of helping primates to readjust their sleeping positions before dozing off so they did not fall out of a tree or get hurt during their slumber. 
It is known that nicotine and caffeine can impact the body’s ability to fall asleep naturally and stay asleep. The chemicals in these products can prevent your brain from reaching deep sleep and instead startle your brain from time to time. 
Anxiety and stress:
It is known fact that the stress or anxious thoughts and worry can keep your brain active, even as your muscles try to relax as you drift off to sleep. This can cause your brain to send out alert signals as you are dozing or even while you are asleep. If you start to experience more jerks or twitches, then you may develop anxiety about sleeping because you begin to worry about these sleep starts. 
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