Every time I see that clip I love it more.
Is that normal for the breed?
Yep. Mastiffs are very large. It takes some energy to get all that mass moving, so mostly they don’t and normally spend a lot of time sleeping. They’re capable of incredible acceleration over short distances when motivated, but it has to be pretty serious motivation. When they do get into motion they can be terrifying and you suddenly understand why they were used for war and for hunting large, dangerous game