It's a puppy thing, every puppy I've ever owned had frequent hiccups as a puppy, very cute and very normal! I call 'em the "puppy hics" and Rem had them a lot when he was younger, he's now 5 months and gets them once in a while.
redundant but I'll say it again.... completey normal. Any dog of any breed we've ever had always had hiccups like crazy as a puppy. My husband always says it's a growth spurt which I know is an old wives tale but I just go with it and they generally grow out of it when they are older and done growing by leaps and bounds like they do now.