Dos screen sometimes doesn't fully start. Then is ok on restart?

A couple of time now my PC (FROM BEING SWITCHED OFF) has been turned on the black and white DOs screen with the yellow logo (phoenix or something) in the corner. Normally it just starts running, showing processor info etc. However a couple of time has just stuck on the first "paragraph" and not run. I have had to switch it off. It normally then just runs straight away. I have had no other "boot" style problems before, and last few days hasn't reoccurred. The only slight thing I have ever had trouble with on the PC is the on/off front switch has been a bit "sticky"... calling Geniuses!!

Any thoughts??

smudge.1969@hotmail.co.uk