Brief Answer:
muscle sprain in neck, muscle relaxant gel application, isometric exercises

Detailed Answer:
hi
There is a clear history of muscle strain in neck.
Actually muscle strain at times takes long to heal.
You may consult an orthopedic doctor and have an x ray of neck done for diagnosis-probably some spondylitic changes can also be ruled out in neck
Muscle relaxant gel application is helpful and some mild physical therapy of neck like isometric neck exercises under a physical therapist
It will settle in few days
best wishes

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Brief Answer:
regular exercises to build tone in musces

Detailed Answer:
Thank you for the queries

Actually nap has nothing to do with your 'zap'--it is when we are about to fall asleep the body muscles go into a relaxation phase and by sudden call from somewhere or awakening for some reason or the other and trying to move or changing posture contracts the muscles of the concerned region and this onset of contraction wave from incompletely relaxed muscles cause jarring of the two opposite functions producing a jerk sort of thing to the moved muscle often leaving a strain or sprain of few fibres of muscle to account for pain and mild inflammation.This is a physiological phenomena over which there is little control.

It is advisable to do regular exercises to regulate muscle responses adequately.
Do show to an orthopedist however and apply relaxant gels

thank you

Regards

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