Hi weearchiesmum. We've had variations on this type of problem at one time or another, less so now dc is 3yo but sometimes he still isn't the slightest bit interested in getting dressed and will wander around doing anything but.
I wonder if your dc wants to be more involved and gain some independence, and this is his way of asserting himself? So you could try letting him slowly start to learn how to put a t-shirt on for instance? Or choosing which trousers he's going to wear today? Just injecting a bit more independence in for him. Or try turning it into a new challenge - ie. you can get a treat/reward if you can get dressed in 20 seconds flat...or just making something funny about getting dressed/having nappy changed. We've done various silly things, eg ditties we always sing at these times or holding up in the air after putting trousers on like they're a superhero flying and saying "superhero!!" - just stupid little habits that lighten it up and make you all laugh.
We did go through an awful stage of not wanting to get dressed though, mainly not wanting to put trousers on, which was a real pain, but dc was older than your dc about 2yo maybe. We had lots of show-downs as couldn't always guarantee we'd be able to leave the house, although I did have a few occasions of saying "fine, if you won't put your trousers on, go out in the snow like that then..." It was a really irritating period but did pass thankfully.
Sometimes with this though, i just think you have to be strict - forget the rewards, forget the distraction - and just go for putting your foot down and showing you mean business and that some things in your daily routine are non-negotiable, sometimes they get the message 'not to go there'!