What's the actual sampling rate of an ADC that is only enabled periodically?
That kind of sampling will lead to aliasing with something roughly like a sinc response if there is frequency component in the input above \$\frac{1}{2(T_{en\_adc} + T_{other})}=\frac{f_{en\_adc}+f_{other}}{2}\$. The shorter the bursts of samples in relation to the entire cycle, the closer it it will approach simply sampling at the lower frequency.