Thumb and index finger will suddenly contract and move inwards towards my palm. is this twitching, tremor or what? it happens after i use my hand

Muscle cramp/spasm: A sudden cramp in your fingers can cause this If all your fingers do it it is called carpopedal spasm which can be due to a problem with calcium levels in your body. This is less likely when only 2 fingers are involved. Muscle spasms can happen if you don't do an activity much, then do it more than you you usually do. I get it when digging many holes for bulbs/plants in the fall/spring.But see MD