Why do I keep getting the same numbers in a loop?

I am creating this a discord nitro gen. It's just for a Rick Roll and stuff. How can I change seed every time it loops?

l = input("How much codes u need to mine?")
passlength = 16
s = 0
possible_strings = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890"
random.seed()
randcharlist = [random.choice(possible_strings) for i in range(passlength)]
code = "".join(randcharlist)
while int(l) >= s:
    s = s + 1
    print("https://discord.gift/" + str(code))