No. 😁
Ebay may send your details to HMRC but HMRC won't give two hoots about you.
Providing of course you are just selling only your own old clobber (and none of those single sales was over the CGT of £6000. ; though I'll admit that's unlikely on ebay! )
If though, you got hold of a box of brand new gadgets and decided to sell multiples of those on the same account, that might raise tax-inspectory eyebrows....