Separation Anxiety?

Drew has been going to stay with Mawmaw since the beginning of January and I am starting to think the boy has separation anxiety.  He literally recognizes the way the car sounds/feels as soon as we turn into her driveway.  He starts crying and he cries until I leave.  He does willingly go to Mawmaw and bless her heart she has the patience of a saint!  She says most days it takes him about 10 minutes before he will start playing...sometimes with other kids, sometimes by himself.  He cries again as soon as I get there to pick him up.  This makes naps quite non-existent on Tuesday/Thursdays b/c if I attempt to leave him in his bed for a nap he wakes within five minutes screaming.  I've resorted to laying with him and the boy sleeps like a log...