Is my labrador puppy sleeping too much?

Some seem to need more sleep than others. As long as it shows periods of energetic play between naps, it should be OK. You could ask the vet since you should be in for shots before too long. For other useful information, check the ''What does a puppy need?'' sticky at https://www.askmehelpdesk.com/dogs/information-articles-our-dogs-expert-labman-53153.html#post251802

is my labrador puppy sleeping too much?
Well, my puppy is a mix and she is 13 weeks old. When puppies are 0-14 weeks old, they need a total of 18-20 HOURS of sleep!

I wouldn't take that 18-20 hours very seriously. Many sleep much less than that.