Why the phase response of a series RLC circuit plotted against frequency goes from 100 to -100 degree?
Why the phase response of a series RLC circuit plotted against
  frequency goes from 100 to -100 degree?


It doesn't.

It goes from +90 degrees to -90 degrees.

At very low frequencies XC is very high and XL is virtually zero hence the circuit can be regarded as a series capacitor and a load resistor: -




At very high frequencies XL is very high and XC is virtually zero hence the circuit can be regarded as a series inductor and a load resistor: -




Source of pictures