Can oral cancer symptoms come and go or are they permanent?

Permanent. Mouth cancers typically start as a lump, bump or patch in the mouth that does not go away after a few weeks. However, not all lumps, bumps and patches are cancer. If concerned, see your dentist or PCP for examination.
Not episodic. If there are any symptoms, they would be continuous.
See below. Once cancer has established itself, then the symptoms do not come and go. They will progressively get worse as the cancer tends to grow( it does not regress or go away (on its own).