Is it possible to construct an autoaction which will reset the field values of several fields at once?
No, not currently but I am looking into it for a later release. In the mean time you can try using a Query action and just update _comprofiler with a database query. Example as follows.
Code:
UPDATE `#__comprofiler` SET `cb_field1` = '[cb_myfield1]', `cb_field2` = '[cb_myfield2]' WHERE `id` = '[user_id]'
forge.joomlapolis.com/issues/3989