Not starting properly?

[Johnny55]

Hi all,
New to the group.
I have had a Boxster 3.2S now for about 9 years and it has never really given me any problems.
Due to having an RTA in my daily driver, I have not been able to drive it for a few months, so it has stood.
The Alternator had failed, so I had that changed, and it started to drive it back from the garage. This was a brand new 150A alternator.
I went to start it yesterday, and it would not start immediately. It would unlock, all lights would come on, but nothing on the key turn. after a few (lot) of attempts, it started.
Did the same today, but instead of keeping on trying to start, I put the jump leads on it, and it fired up straight away.
I was initially thinking it may be immobiliser related, but the fact that it started straight away with the jump leads makes me think maybe starter motor?

If anyone has any thoughts I would appreciate some input.
There are no diagnostics anywhere near me as I live in very rural Norfolk!
Thanks in advance.
J.