middle of the night crying/sobbing 21 mos old

[e_roehm23]

Ever since the time changed ( i don't really think this has anything to do with it, just that is the exact night it started) ds who is 21 mos has been waking up in the middle of the night and sometimes early a.m. just wailing!  He has always been a good sleeper.  He sleeps in his crib in his own room with the door shut to keep it quiet for him. We keep a music box playing at night.  He is our first, so we're new to toddlerhood.  Anyone know what would be causing this? 

[Cativari]

I have a little boy who does this as well. For us it usually signals a growth spurt, either developmental or physical. these phase last until the growth is over. a few times it has meant that he's been stressed out usually by a change in routine or just being out too much. Also being sick will do it to him.(his dad talks in his sleep when sick too)

Eta: Kai is asleep when he does this and doesn't remember anything in the morning