Why I don't experience any  side effects after I get my 1st shot of covid-19 vaccine?

Most people will not have any side effects from the vaccine.  A few will have a slightly sore arm for a day or two.  Very few will experience significant effects.

The stronger your immune system is, the faster you'll feel side effects of your immune-responsiveness. Not getting a symptomatic response is considered normal. Give it another day or so, you might feel it a little.

Feeling side effects just means its working better for you than most people.

Because some individuals have no side-effects

No one I know got any side affects.

Just guessing.  

Your immune system is probably strong. Got mine yesterday Phizer vaccination 5:45 pm eastern time.  Just mild injection site tenderness. Nothing else. My first spring time mosquito bite on my forearm is bothering me more.

Some do, some don't. ...after I GET or after I GOT?

you stated in PAST TENSE: "Well I got vaccinated..." and then "...how come I don't..." where it should read in past tense as well  "...how come I DIDN'T..." or is it a continuous thing that you keep getting vaccinated and DON'T experience side effects? So confusing... from an engineer.

Most people don't experience any side effects .. my 87 year old mother didn't.

Why, do you want some side effects .. just to give you something to moan about ?