When I restart my computer Grey screen with restart message

My computer was running slow. I had not shut it down for several days. I went to shut it down and it gave me a grey screen with the spinning wheel. This lasted for a few hours. I then used the power button to shut down the computer. When I restarted, It showed a grey screen I hear one start-up chime and then some (DOS Language) in the background with a black box in the foreground stating I had to restart My computer by holding down the power key until it shuts off and then restart by pressing the power key once again. Sorry for the run on sentence. I tried this several times, Shut down and restart, all with the same results. Any suggestions.

Corey