My 6 week old kitten is acting like it has little to no balance falls over when sits up his whole body shakes he gets stiff and then falls to the side he is aggressive or scared not sure could these be symptoms of a poisoning by chance

Not a sign of poisoning but are symptoms of distemper. He is scared most likely. Time for a vet visit. This sometimes happens in the runt of the litter, the one born last that didn't quite get a chance of much nutrition and immunization of the queen's milk.