Lately my mini has been struggling to start, but only if i leave it overnight, it cranks when i turn the key but struggles to start, it eventually starts, but after a 2-4 seconds while holding the key

Today though, i started it after not using it for 3 days, and i took a while to start, and started, but when it did, it acted like if it wasnt recieving fuel or like if it just wasnt being able to stay on idle

I just pressed the accelerator, and it revved up and then went to idle perfectly

The car runs flawlessly after starting, but struggles at start, only after left overnight

Anybody know anything? I believe this could be an electrical problem with ignition, i doubt it is the fuel pump, although i could be wrong, battery is brand new and is perfectly fine as i did a battery test on it and tested perfectly

Thanks