Wierd start issues

Afternoon all!

Had a wierd problem start! Got in the car Sunday to pop to the shops. Key in, knocked the blowers on and turned the key - nothing.. no starter engagement at all. Lights didnt dim. Few turns of the key on and off and on about the fifth try, she started.Rest of the day, on and off without a problem. Out to her Monday morning 5am, no start again.. same story, 5 or 6 times on and off and it started, no problems for the rest of the day.Tuesday morning it started first time, but thinking back i literally got in the car and turned the key straight away, no ignition on etc. This morning was a bit harder - a good 15 times before it would start.Quick search suggests the wire under the battery tray, but i thought the problem would be constant, not just first thing in the morning and then fine the rest of the day?Or Starter? Possibility of it being the battery?

Edit - quick think back last week car was sat for a couple days and she felt a bit weak on the start-up but got going..