I cannot see your image but if its a switched capacitor amplifier, try the periodic steady state analysis to get the periodic operating point, and then do a periodic noise analysis. This is of course only possible if you have spectre RF. Or else, take both the on and off states and do a noise analysis on each state using a regular SPICE simulation
A coarse calculation can be include the thermal noise and OTA input refered noise. Then the 2 noise power transfer to the output node by charge transfer action during hold time.