You've got yourself a half-draft (or at least partial draft) of some sort.
A lot of half-drafts come from the mistaken belief that if you cross "hot blood" (like a Arab) with "cold blood" (like a draft horse) that you magically get a "Warm Blood" that will be worth $100,000.
Sadly, such is generally not the case. So these "breeding experiments" get sold off. Sometimes they're good horses and sometimes they're not. You're looks OK. The "nervousness" that you mention can be the result of a lot stuff ("nervous DNA," over feeding, under work, poor fitting tack, etc.). Sometimes it's just a function of age (how old is the horse?).
As to gait, maybe so and maybe not. A video would show a lot.
Good luck with your horse.