Sagittarius on the inside, Aries on the way in.
Your sun in Sagittarius (fire, mutable) is the engine — what burns at the centre, what adapts when you are at home in yourself. Your Aries rising (fire, cardinal, ruled by Mars) is the door — the way you arrive in a room, the first read the world takes of you, the body you walk in.
Strangers tend to assume you are fast and bold — that is the Aries arriving first. Then they get to know you and discover the Sagittarius fire underneath, which can be reinforcing — same flavour, more of it.
Reads as Aries until you trust them; then Sagittarius comes through. The mutable-cardinal mix means you adapts on the inside while starts on the outside — internal and external rhythms are different, which is its own work.