Very volatile ROAS

Hello,

I am new to selling on Amazon (started beginning of November 2021) and therefore also new to Amazon PPC. I have a Sponsored Product campaign which I spent most of the first month playing with to optimise it (as best I could with limited data!) and trying to understand it. The last few weeks I’ve pretty much left it alone so it’s more stable, and I haven’t changed my listing or pricing much in that time. But I’m noticing my ROAS is incredibly volatile and wondered if this was normal. For example, the last few days of orders on my campaign is 4, 8, 10, 4, 3, 15, 2, 0 (I understand the last few days may not be up-to-date yet). As I said, this is without changing much (if anything). For confirmation, this is using my entire £100 budget each day. I understand it is kind of luck who clicks on the link and if they buy it, but it seems a bit volatile. Does anyone have any advice or insight? I know I would be better off having weeks/months worth of data rather than days but for now this is what I’m working with.

Thanks in advance,
Adam