Crying when waking up?

So my LO has always been a great sleeper, he started sleeping pretty much through the night when he was 5 weeks old. Recently though we’ve been struggling with what I think is a sleep regression, and the worst part is waking up. He’s started to cry when he wakes up, but only in the morning! He’ll wake up a few times at night but I usually can just nurse or cuddle him back to sleep and he never cries when he wakes up at night, he just fusses and rolls around till I wake up lol. It’s so weird, even if he has a great nights sleep, when he wakes up in the morning it’s like he doesn’t want to actually wake up so he starts to wail while he’s still asleep, and I have to pick him up and gently coax him awake. I thought it might be gas cause we just started solids, and we usually feed him one solid food meal at 6:30, then bedtime is at 8:30, but once he’s awake he’s happy and smiley, doesn’t seem to be in any sort of pain or distress anymore. Has anyone else gone through something like this?