Lab started barking like a lunatic, help!

[BaconAndAvocado]

Our 18 mo coco Lab is usually a very laid back, biddable, generally great to be around pooch.
However, over the past couple of days he has started barking incessantly when we sit down and leave him to his own devices. In the Before Times he would go and lie down, play with/chew a bit of bone, be happy to be cuddled next to one of us on the sofa.
What’s happened?!
He’s not been neutered yet but doesn’t try and hump us......he just barks!

He had double elbow dysplasia surgery in early October but recovered very quickly.

The only thing it might be is that he needs more walks? He’s just started going off-lead since his op and gets just over an hour’s walk including some times off-lead on the beach. This walk is mid morning.
He was previously ok with this set up....do we need to take him for another walk early evening?

Labradors are energetic working dogs - he may need more exercise, but I suspect he also needs some mental stimulation too as you haven't mentioned doing anything with him in your post.

I play Brain Games with him where I get a blanket and hide snacks in it. We do training:wait, down, roll.
Any other suggestions?

18 months, you say? Classic age for teenaged tantrums and forgetting all their training. If you’ve ruled out a medical cause, I’d suggest it’s to with him hitting the teens phase.

I would say that 1 walk a day is a bit skimpy but then I’m not sure on what advice you’ve had re elbows. I’d add in a short, sniffy on-lead walk in the late afternoon (15-20mins). Give him a chance to have a calming sniff but also tire out his brain a bit. Then work on your settle training a bit.

It’s really normal for labs to go a bit silly at this age and forget all their previous training. They do grow out of it if you stay calm and persist with their training.

I'd say he needs a fair bit more than that, though I'm not sure what else you can do with his elbow issues - is he able to be properly mobile now?

Because they're such great pets, I think it's easy to forget that labs come from working stock and need a fair bit of engagement to settle, especially when they're young.

I would add in things like:

Teaching him to "find it". Start of easy - hiding a ball in a cardboard box in full view, for example, and getting him to sniff it out. Slowly you can make it harder and eventually you'll be able to say, leave him in the garden, hide stuff in the house and send him to find it all with his nose.

Try "ditching the bowl" - feed him all his meals from enrichment toys - stuffed kongs, snuffle mats, lick mats etc. Make him work for all his food and it will tire him out much more than just being fed from his dish. If he's fed dry, you could also scatter all his food in the grass for him to find.

Long, slow sniffy walks. Let him pick the pace and direction (within reason obviously) and just let him sniff. Even if you only get half a mile, 20 minutes of sniffing is equal to an hour of exercise in terms of tiring him out.

If he's physically fit, you could also look at things like agility, man-trailing or even some professional gun-dog training. He doesn't need to go on shoots, but a gun dog trainer will be able to teach some proper work - sits, retrieves etc.

Good luck!