Why does my dog do this?

[Dieu]

Have an unneutered Shih Tzu boy. He'll be 5 years old next year. He adores me, and the feeling is mutual. It's just he, I, and my 3 kids in our family. He is wonderful and we all love him.
He's still a bit puppy like, and has never humped any of us.
Thing is, when I do something out of the ordinary, such as climbing a ladder, dancing, or even just playing charades, he will get quite stressed. He will always pin himself to my leg, not humping exactly, but I'm pretty sure it's a dominance thing. He never, ever does this at any other time.
Anyone else come across this type of behaviour?
Thanks.

You've basically answered your own question; he's doing it because he's stressed. Humping isn't a dominance thing (dominance itself isn't a thing in dogs), it's generally a response to a dog being in a heightened emotional state. Some dogs will hump when they're excited, some will do it when they're stressed and it sounds like your boy falls into the latter category.

If you want to stop him doing it then your best option is to either avoid the situations where he's likely to do it or work on lowering his stress levels. Targeting the behaviour itself may resolve the humping but he'd likely just find another outlet for the stress instead.

Thanks. Thankfully I don't dance and climb ladders every day! Certain things have come to light because it's Christmas, so putting up decs, playing with the kids etc.
He's generally very laidback, so I'm not sure why these situations would stress him out. It's not like it's rough play, or anything like that. Ah well, I guess they all have their own little quirks and foibles.

My dog started doing it whenever I had my dressing gown on, must've liked the smell maybe

Definitely a stress reaction OP, nothing dominance related that theory was eventually disproved by the person who came up with it!

If it isn't causing a problem you can always just keep him out of the way while you're climbing etc, or try giving him a long lasting chew or treat to pacify him and distract him so he doesn't get stressed

My dog does it when he gets excited or if family members hug each other , he’s neutered and 9 , he’s always done it - stops as soon as the excitement / hugging stops