Screwy screen

I have a a new computer barely a week or two old. At nights when I go to bed I shut off the monitor but leave the computer running, and sometimes the next morning(actually this marks three mornings in a row) I turn the monitor back on and the screensaver is off but instead of my desktop the screen is black and few icons are present, this morning this went away when I moved my mouse, other mornings pressing ctrl-alt-del had the same efffect, then I type in the password and everything appears fine once more. But then I try and open a program and the screen will go blank with part of the taskbar visible at the top of the screen, after many frustrating minutes of ctrl-alt-del or pressing the windows buttton I can occasionaly get it to go away only to have it come back when I try to open the start menu to reboot, most of the time I can't though and have to just press the power button, afterwards there are no problems for the rest of the day. Anyone hav any bright ideas