Can I start and stop a tile floor job?
It certainly is acceptable to do a tile job in phases. There's no structural reason that tiles need to have their supporting mortar connected mechanically. The critical bond is to the substrate, not adjacent tiles or mortar. Large residential and commercial tile jobs are done in stages every day, and with no special procedures or materials. 

One caveat might be the grouting. Ideally you'll complete grout work for a room in one step using grout from a single mix batch for visual consistency.