Please review the WordPress codex on how to increase your memory limits here: https://codex.www.ads-software.com/Editing_wp-config.php#Increasing_memory_allocated_to_PHP
This kind of problem is usually caused by either a conflict with your theme or with another plugin.
The best way to determine if the issue is being caused by a theme and/or plugin is to temporarily switch your theme to Storefront and disable all plugins except for WooCommerce. If you can install plugins, install Health Check. On the troubleshooting tab, you can click the button to disable all plugins and change the theme for you while you’re logged in to that session without affecting normal visitors to your site. Note that Health Check may not count Storefront as a default theme, so you can also use Twenty Seventeen as well.
If that resolves the issue, then one-by-one you can switch back your theme and re-enable your plugins, testing in between, until you find the one causing the conflict.
When a new version of WooCommerce is released, we sometimes update the default templates.
This applies to major releases but also to minor releases and themes may break because they override WooCommerce’s default templates. Most theme authors fix their themes in a timely manner, so you only need to update your theme to get the updated templates.
If the themes are not updated, or if you modified the templates yourself or are using a child theme, you need to update the templates yourself.
You can read more about how to update the templates here:
https://docs.woocommerce.com/document/fix-outdated-templates-woocommerce/