Oh dear another 'what's this?' post from me; my apologies beforehand, please bare with me

3 month old pup is now started some odd behaviour at night.
Since the day he was brought home he settled in his crate and has virtually always slept through from 11pm-ish to 6am.

There have been no changes to his routine at all throughout the day; feeding is the same, exercise and play still regular, so I can't initially put anything down to a difference in his daily activities which may have triggered the following.

For the past few nights now, he has woken us up by 'digging' in his crate; it's incredibly noisey and firstly we assumed he was playing with a toy or just making his bed comfy, but this is then followed by a few whimpers if we don't go to him and more digging.

First couple of times it happened I assumed he may need the toilet, so I let him out and sure enough he went outside, did a pee, came back in and popped him back in the crate.
However, the same thing occurs then throughout the rest of the night (or morning rather ) until he is let out indefinately and the house is awake.

I've noticed there does seem to be a pattern as it appears to be on or around 3:30am when he first does it, then around an hour/hour and a half every time after that til I'm back up at 6am.

Any ideas?

Thanks in advance.