Samsung U600 helppppp?

Well, my phone had been working fine, then all of a sudden when I took it out of my pocket, the phone was on and the screen lit up but it was blank. Nothing came on....nothing. I turned it of then back on....nothing. I took the battery and sim out and out it back in nothing. Then all of a sudden it started working...so i thought it may have been nothing. Few minutes later the same thing happened, it's on but a blank screen...what can I do?