What are three reasons the war of 1812 started

There were several causes for the U.S. declaration of war: First, a series of trade restrictions introduced by Britain to impede American trade with France, a country with which Britain was at war (the U.S. contested these restrictions as illegal under international law); second, the impressment (forced recruitment)

Explanation:

Britain's seizure of American ships and impressment of sailors.

America's resentment of Britain.

American belief that British were arming Native Americans and inciting them to riot.

American "War Hawks" wanting to annex Florida and Canada.