Sorry for the misunderstanding with my previous reply.
If you have to configure ADC in software trigger mode (when SC2[ADTRG]=0), then you may need to write SC1A[ADCH] values one by one for ADC0 and ADC1 respectively to achieve ADC sample.
But I think you can configure ADC in hardware trigger mode (when SC2[ADTRG]=1), and select PDB trigger ADC. Select software trigger for PDB, writing 1 to PDB_SC[SWTRIG] resets and restarts the counter of PDB.
For more detail please have a look at 43.7 ADC Trigger Sources of S32K-RM.