boxster starting problem

[robstuartuk]

Hi all I have a boxster 2001 2.7
Over the last couple of days I've had a little problem starting.
It normally turned over right away and fires up but last week i struggled for a couple minutes getting it to fire up. It turned over ok and and spluttered a little. But wouldn't fire up.
After a couple of minutes it eventually started and was fine for the rest of the week.

I've left it for 2 days and gone out today and same again turns over has the odd splutter and won't fire.
After about 5 minutes ive drained the battery so now need to charge.
Question what could the likely problem be?
I have noticed the last week or so before the issues with starting it would do the odd backfire when overtaking.

Thanks in advance all..