Just showering everyday shouldn't cause hair loss as long as you don't wash your hair during every shower and even then washing your hair everyday shouldn't cause hair loss either but I guess it's possible.
It is normal to lose a little bit of hair when you wash your hair so you do lose some hair when you shower if you wash you hair.
Washing your hair everyday can dry out your hair and strip your hair of essential oils that are in your hair which keep your hair shiny and healthy.
Washing your hair one or twice per week is good enough for keeping your hair clean and healthy.
Showering everyday is fine and good to keep your body clean and smelling great.