Talk to General Physician on Sudden Shivering At Night Time Before Bed Time

Assalaam u alaykum. Yesterday i was perfectly healthy and fit,then did ablution wuzoo for prayer and stood on prayer prayer i suddenly started unbearable cold and my all body started shivering so much that i couldnt complete prayer. Then i went to bed covered with two blankets. When body became hot i felt normal. Now i woke up around 430 am and offered prayer after ablution having no shivering .But yesterday night immediately after shivering i had one loose at 445 am i again had semi formed very little cough but phlegm is continuously coming in my mouth and i swallow it. I must mention here that its not the first time i experienced this shivering.i have experienced it many times in past as well. I also got my calcium level tested around 7 years ago for sudden intense shivering at was normal. I dont get fever no issues just very severe shivering after every few years at night before bed goes after few minutes. I must mention th