I am currently in the process of an SSBI for a TS clearance with my current employer and OPM is conducting the investigation. If I take another job that requires the same clearance by OPM, will they just resume my current investigation until I begin work with them or will I have to start over?
Most likely the investigation process will continue. Only thing that may happen is if you leave the employer before the BI conducts the enhanced subject interview. In which case, you will explain that you left your current job for a new one after completing the questionnaire.