My impereza of 2000 chokes and backfire slightly when i start the engine for 2 to 3 minutes then its fine until i start again Please help if you know what the problem could be?

It may be time to inspect and clean or replace the spark plugs. When the ignition key is turned to "ON", the fuel pump builds pressure so the engine may have enough fuel to start. If the plugs are fouled or don't provide enough spark to completely ignite the initial fuel with pressure, the engine will choke, backfire, and sputter until the pressure is stabilized. After the initial startup and the fuel pressure is stabilized, the plugs ignite the fuel enough for the engne to run smoother.