My Professor Acts Strangely Towards Me...?

I've taken two courses from my Psychology professor but this semester he's begun to act wierdly towards me. Sometimes he'll be very gruff and cynical or simply ignore me in cl. Other days he'll be quite friendly and approachable. He often asks me difficult questions in cl but I do try very hard in cl so I tend to answer them correctly. There's not a day I dont get asked at least one question regardless if it's a gruff/mean day or a normal one. It wasn't this bad the previous two courses...also my grades have not slipped nor can I recall doing anything that may have been considered improper or rude...It really bothers me because I do find his course material very interesting and also I have enjoyed his previous cles...