Why do i sweat a lot? i'm just sitting down and i start sweating bad in armpits

Hyperhidrosis: Hyperhidrosis is the condition characterized by abnormally increased sweating/perspiration. The cause of primary hyperhidrosis is unknown, although some physicians claim it is caused by sympathetic over-activity. Stress has also been a possible cause. There are medications that can help. Best wishes.

See a doctor: See a doctor and get checked ands ee if they want to do some blood tests.