4 month old trashing but desperate to sleep

[thundernlightning]

Hi all, maybe you know what's going on. My DS, 4 months, has just learned to roll and sit up all in about 48 hrs and now it's like his body can't stop moving, even though he's exhausted. I just swaddled him and snuggled him to he couldn't thrash and he's gone out like a light, so I know he was exhausted. It's just like he couldn't stop moving.
Has anybody else had this? What causes it? How long should I expect it to last?