P.M.
How puzzling and anxious this behavior must be for you. Your little boy sounds like he's able to ask for what he wants, but he may simply not know what he wants when he's just waking up, possibly somewhere between a dream and the "real" waking world. (Every once in awhile my 4yo grandboy has an unexplained meltdown, too. Puzzling, but then life goes on and he's his usual, sunny self.)
Try talking to him sometime during the afternoon, when he's in a great mood. Ask him what he would most like from you when he's feeling so upset in the morning. Come up with a "plan" in which he participates (subject to change depending on how well it goes).
If you can, work out a soothing symbol that he can cling to, like a favorite toy, until you are able to get to him (he may already be feeling too much distress for easy soothing by then). Make up a playful story, maybe about how this stuffed toy runs fast to his little boy when he hears him waking up, because he wants to help make him smile. Use imaginative language to talk about the positives of waking up safe in his own bed, warm and cozy, with mommy and daddy nearby and his toys there to help him smile.
Kids this age are beginning to connect with make-believe, and it can become a powerful shaping force over the next few years. Use it to your advantage. And don't be discouraged if it doesn't take right away. Like all new life skills, this will take some practice on your son's part, and some experimentation on yours.