Monitor Problem

My monitor display has recently started to play up for no known reason. It keeps resizing itself ever so slightly (sometimes several times rapidly) but as you can imagine this can get very annoying. Also there is a faint line that keeps rolling up from the bottom of the display to around half way up. This only happens every so often.

Can anyone offer me any advice as to what may be causing this. Do you think it is something minor that can easily be fixed?

Thanks for any help,
Jason.