S.H.
Yes, it's a phase.
Both my kids have gone though this.
It will pass, and it will go back to normalcy.
really, he is not doing this on purpose to irk you... main thing is he does go back to sleep on his own, and can entertain himself, safely in his own room.
Which is good.
Would you rather him be needy and crying at each waking and THEN come barging in on you in your bed, and screaming for you to play with him? So, be glad he is just in his room, playing with his toys by himself. He is showing self-motivation and self reliance.
It's all about ages & stages. Lots more will come.
They are just changing so much internally... 3 yrs. old is a hard age anyway. It's much harder for the CHILD to adjust too, versus the parent. THEY are the one's changing... growing pains.
All the best, take it with a grain of salt.
It'll be okay and your son is normal.
~Susan