Flat battery?

[CopperBolt]

Hi
Over the last 2 weeks if I leave my car unused for 3 or 4 days when I go to start it it sluggishly turns over and won’t fire. I have to turn off ignition, try again and repeat. Usually it will start on 3rd or 4th attempt. This is the first time it’s done this since I’ve had it, about 4 years.
Could it be the cold weather making the battery “die”?
When it does start a yellow light that looks like skid warning is on on the dash. Once I’ve driven a way and stopped it will usually start again ok and the the yellow,light is no longer there.
Car is an 09 mx5 2 litre. 27000 miles on clock. Driven very low mileage each year, even less In lockdown.
Grateful for any ideas/advice.
Thanks

[CopperBolt]

Cheers all.
I suspect the battery in there is the original fitted at the factory in 09.

I don't own a battery charger so not sure whether to try and borrow one(no one I know has one I don't think) or just get a new battery sorted.

Was reading up on MX5 battery change and apparently it's a pita if there no lifting strap on the top as its wedged into its slot pretty tightly. Will have to have a quick look.

If I charge it do I have to disconnect the negative or positive side first?

Thanks

[CopperBolt]

Sorry to keep bumping this.
Been out to look at the battery. Its got a sticker on the side saying fitting date, numbers 1 to 12 and then 2018,2019,2020,2021 . So I would guess this battery was fitted in 2018 some time? They wouldn't put that sticker on it in 2009....

So Im wondering now if a good charge will sort it. Or is 4 years my lot.

Can I charge it without disconnecting the wires to the battery in the car? Don't want the stereo to lock me out by asking for an unlock PIN which I wont know or anything when I reconnect power.

Thanks.

[CopperBolt]

Cheers all.
Had it on charge for 6 hours or so. Just been out and disconnected charger. Started first time.
Will see what it’s like after minus temperatures tonight in the morning.