My husband and I brought home a Sheltie puppy about a week and a half ago. He's 13 weeks old. Last night, we had some friends over, and he was very excited to meet everybody, running around to get patted, etc. All of a sudden he started making humping motions - not on anything or anyone, just humping the air!! He has never done this before! We took him outside to walk around the block and calm down. It looked funny but I'm wondering if it's too early to have him neutered. He was just at the vet a week ago and she recommended around the 5-month mark. Has anyone else experienced this? These were his first visitors in our house - is it a dominance/protection issue? He didn't appear to be intimidated or bothered that we had friends over, quite the opposite actually.

I dont recomend altering until 5-6 months either.
What he was doing is totally normal. Between the puppy hormones and all the excitement, puppies respond in different ways...some more embarrassing than others, lol.

The humping has nothing to do with being intact or ultered. It is normal for some puppies to hump eachother or objects (like stuffed toys) We tend to see puppies or dogs do this when they are a little shy or more on the submissive side (Less sure about themselves)
The best way to deal with it is to simply redirect the puppy to something like a bone and praise the puppy for showing interest in the bone, don't give any attention(like petting or any verbal) for the humping.
Also, basic training everyday, with lots of praise for good behaviors will boost the puppies self esteem, which may in fact lessen humping.
Good Luck!
Sue