Your first thing to check would be corroded battery posts.
patrick bailey had this to say:
>Yesterday I drove into town about 40
>miles and parked for about 1/2 hr and
>she wouldn,t start no starter at all not
>a click nothing.The battery was up so I
>tried a couple of times and it
>started,drove it home and it started 3
>times no problem.Now I'm thinking (1)
>bad ignition switch (2)bad starter
>solenoid (3) bad ground somewhere.Any
>ideas it's a '79 B It wasn't too hot
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the red one with the silver bootlid.