the battery is old
> though, could this be the problem?

Old is a relative term.... 3 years? 5 years? 7 years? ... look at the top of
the battery and there should be some numbers punched out that would give you
some indication as to what year the battery might last until.... but,
personally, living in a very cold climate,,,, if I had a problem like this
and the battery was about 5 years old I'd just replace it before going into
a winter.... batteries don't cost that much compared to the convenience of
not being stranded on a cold and snowy day :)

but my guess is your problem is of an electrical nature... I might look in
this order: ground connections, ignition switch, starter (solenoid could be
going bad)...

Bill