The famous scarcity timer is often represented with a flame and urges the customer to complete their checkout. Follow those steps to show the burning timer on your checkout in Shopify:
In your Shopify admin panel, select Apps > TeleCheckout.
Scroll to the section called Marketing.
Check the box Display a scarcity timer and press Save.
You can customize the text, see above section: How to add custom text on the checkout page in Shopify Basic?