this could be linked to one of any number of issues, faulty wall socket, bad connection where the three core cable attaches to the filter etc, you need to take the top off next time it refuses to start and see if you have power at mains filter, if you have its more than likely that the start relay is faulty it may be glass encased in the top section or r.h side where door striker enters which needs taking side panel off to access
keymatic, March 2012