For auctions or offers if the seller requires a payment method in advance, you may have to provide a payment method that can handle a reversible payment hold. That payment method will be remembered by eBay for the next time you need to provide a payment method for an auction or offer, and that method will be indicated on your eBay Payments page as "for offers and auctions".
If you mean that when you check out of eBay and select PayPal, you are sent directly to a specific PayPal account without entering username or password and you do not want that to happen, sign in to that PayPal account outside of eBay and use the Gear icon to go to Settings and choose Security, then check the "Manage your Logins" and "Auto Login" sections and either delete those entries or select "Log out of all devices".
If you are unable to sign in to that PayPal account directly, try using a different browser (or a private or incognito browser window) to see if that gives you the option to select a PayPal account.
If you mean that when you check out of eBay and select PayPal, you are not able to choose a specific payment method in your PayPal wallet but one is automatically selected for you, in that case go to your eBay Payments page in your eBay account and delete the entry for PayPal that appears there.
https://ppcapp.ebay.com/myppc/wallet/list
The next time you check out on eBay and choose PayPal, you should be sent to your PayPal wallet page and given a chance to pick a specific payment method.
