Why does the drill operate intermittently with about a 10 second pause.

The most likely cause of interruptions while the device is working, that is, after it has started once, is the carbon brushes being deformed in some way causing the contact it needs to sustain to become intermittent. I say that because the drill will fail in two places 80% of the time, the starter, (the trigger and associated circuits) or the carbon brushes. Both are easy to fix and both can look similar unless you remember that if it is having trouble starting, its the trigger, if it starts almost immediately but anything goes wrong while its functioning, (slowdowns, stoppages, sparks, smoke; The four esses) than look to blame the carbon brushes.