Screen flashes

'Woke up' pc from sleeping...everything just start flashing. I clickd on/off and I was finally able to go to e-mail/websites.  I did go to 'Support Assist'..   Scan Hardware stopped at 92%, indicating an error occurred and could not finish.   Then my pc worked fine.

I closed the cover for a couple of hours,   then opened it and went to e-mail.  Everything on screen was 'jumping' around.  I was able to click  restart. Dell appeared, but red lines on left  and green on right.   Turned it off and on again...screen then flashed from black to blue, turning off and on intermittently. 

I then turned it off for quite a while.  Turned it back on and I was able to, again, use my pc.  HELP!