Hi SEH,
in the past you definitely had to be three when you started
kindergarten, but I think some places are now taking the younger kids too. Generally those places are probably private Kigas, though. If your child is 1 1/2 - 2 1/2 you will probably need to find a Kita (Kindertagesstätte), also called a Krippe. You have basically NO CHANCE of getting a spot in one of the public Krippen -- my daughter is 16 months old, has been on 5 or 6 waiting lists since before birth, and still didn't get a spot this September at a public place.
Most public Krippen in Munich have waiting lists of 300-600 children. You have to sign up for the waiting list in person at each individual location, on Monday afternoons between 2:00 - 4:00. That's the only time. You do also have to be working to have any hope of ever getting a spot, although they never asked me for proof.
Once your child is already three, you have a legal right to a Kindergarten spot the following September (not necessarily at the Kiga near your home though!), but you do not have a legal right to a Krippen spot before that time. I am not sure what the sign-up rules are for the public Kigas because my daughter isn't old enough yet.
Hope this helps.