Convert checkout button minicart to a simple link.
Add a light background colour (e.g. #f0f0f0) or bold the text when a product is added to bag (bag has item).
SHOPPING BAG IS EMPTY:
Despite having such visual prominence, the red checkout button does little for users who don't have a product in their bag yet. It does not necessarily motivate browsing or trigger any action - specially to visitors landing on a product page as the point of entry. It is very similar to the 'Add to bag' button and unnecessarily competes with it for attention.
A user who intends to shop and has added products in their shopping bag is likely to be committed enough to visually scan the page for a shopping cart icon, cart or checkout link when they are ready.
SHOPPING BAG HAS PRODUCT:
After a user adds a product to cart, triggering or facilitating the checkout process may be desirable (depending on whether the goal is conversions or increasing basket size). Whatever the implementation, it may help to draw some attention to the checkout button. We suggest a light background or bold text.
A/B Testing is recommended to detect changes and correlations and establish causality between the checkout button clickthrough rate and % Visitors who started checkout and Average number of products in cart or Average order value.