Just a hunch, but it sounds like you have a canvas gi. They will eventually get more relaxed. After a year or so.I recently got a new, heavier-weight gi. The brand tag says MAP2. My older gis from this brand are as soft as an old T-shirt, so I tried washing it several times. It's still very, very still, so I tried some tricks I read about online.
1. Washed the gi five times in warm water and tumble dried it.
2. Added a generous amount of fabric softener to one wash.
3. Added 1/2 cup of baking soda to the wash water
4. Tried tumble drying in the dryer with a large ball of aluminum foil
It's a little bit softer -- maybe 5 percent -- but the arms still want to stick out when you hand the gi on a hanger.
Anyone have any advice on how to soften up the material, shy of just wearing it to a few hundred practices?