PHP Notice: Undefined index

Hi,
I'm seeing a bunch of Undefined index notices on every page load, any way to address this?

[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: spider_flag in .../includes/classes/observers/class.products_viewed_counter.php on line 37
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined variable: spider_flag in .../includes/application_top.php on line 223
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: shipping in .../includes/modules/payment/paypalwpp.php on line 1537
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: customer_id in .../includes/modules/order_total/ot_group_pricing.php on line 88
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: customers_group_pricing in .../includes/modules/order_total/ot_group_pricing.php on line 89
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: customers_group_pricing in .../includes/modules/order_total/ot_group_pricing.php on line 91
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: group_percentage in .../includes/modules/order_total/ot_group_pricing.php on line 93
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: customer_id in .../includes/functions/functions_taxes.php on line 305
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: sendto in .../includes/functions/functions_taxes.php on line 306
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: entry_zone_id in .../includes/functions/functions_taxes.php on line 337
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: entry_country_id in .../includes/functions/functions_taxes.php on line 338
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: customer_id in .../includes/modules/order_total/ot_group_pricing.php on line 88
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: customers_group_pricing in .../includes/modules/order_total/ot_group_pricing.php on line 89
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: customers_group_pricing in .../includes/modules/order_total/ot_group_pricing.php on line 91
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: group_percentage in .../includes/modules/order_total/ot_group_pricing.php on line 93
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: customer_id in .../includes/functions/functions_taxes.php on line 305
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: sendto in .../includes/functions/functions_taxes.php on line 306
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: entry_zone_id in .../includes/functions/functions_taxes.php on line 337
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: entry_country_id in .../includes/functions/functions_taxes.php on line 338
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: country in .../includes/modules/payment/paypalwpp.php on line 1094
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: countries_iso_code_2 in .../includes/modules/payment/paypalwpp.php on line 1095
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: countries_iso_code_2 in .../includes/modules/payment/paypalwpp.php on line 1097
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: country in .../includes/modules/payment/paypalwpp.php on line 1098
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: countries_iso_code_2 in .../includes/modules/payment/paypalwpp.php on line 1099
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: customer_first_name in .../includes/modules/payment/paypalwpp.php on line 1595
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined index: customer_id in .../includes/modules/payment/paypalwpp.php on line 1599
[24-Jul-2020 07:32:52 Europe/London] PHP Notice:  Undefined offset: 1 in .../includes/modules/payment/paypal/paypal_curl.php on line 576
[24-Jul-2020 07:32:53 Europe/London] PHP Notice:  Undefined index: customer_id in .../includes/modules/payment/paypalwpp.php on line 2910
[24-Jul-2020 07:32:53 Europe/London] PHP Notice:  Undefined index: customer_first_name in .../includes/modules/payment/paypalwpp.php on line 2910
[24-Jul-2020 07:32:53 Europe/London] PHP Notice:  Undefined index: customer_last_name in .../includes/modules/payment/paypalwpp.php on line 2910
[24-Jul-2020 07:32:53 Europe/London] PHP Notice:  Undefined offset: 1 in .../includes/modules/payment/paypal/paypal_curl.php on line 576
[24-Jul-2020 07:32:53 Europe/London] PHP Notice:  Undefined index: RESULT in .../includes/modules/payment/paypalwpp.php on line 2923
[24-Jul-2020 07:32:53 Europe/London] PHP Notice:  Undefined index: RESULT in .../includes/modules/payment/paypalwpp.php on line 2924
[24-Jul-2020 07:32:53 Europe/London] PHP Notice:  Undefined index: L_ERRORCODE1 in .../includes/modules/payment/paypalwpp.php on line 2934
[24-Jul-2020 07:32:53 Europe/London] PHP Notice:  Undefined index: L_SHORTMESSAGE1 in .../includes/modules/payment/paypalwpp.php on line 2934
[24-Jul-2020 07:32:53 Europe/London] PHP Notice:  Undefined index: L_LONGMESSAGE1 in .../includes/modules/payment/paypalwpp.php on line 2934
[24-Jul-2020 07:32:53 Europe/London] PHP Notice:  Undefined index: L_ERRORCODE2 in .../includes/modules/payment/paypalwpp.php on line 2934
[24-Jul-2020 07:32:53 Europe/London] PHP Notice:  Undefined index: L_SHORTMESSAGE2 in .../includes/modules/payment/paypalwpp.php on line 2934
[24-Jul-2020 07:32:53 Europe/London] PHP Notice:  Undefined index: L_LONGMESSAGE2 in .../includes/modules/payment/paypalwpp.php on line 2934
[24-Jul-2020 07:32:53 Europe/London] PHP Notice:  Undefined index: paypal_ec_token in .../includes/modules/payment/paypalwpp.php on line 2806
[24-Jul-2020 07:32:53 Europe/London] PHP Notice:  Undefined index: paypal_ec_markflow in .../includes/modules/payment/paypalwpp.php on line 2818

First question is, why is either configuration->Sessions->Force Cookie Use set to True and/or configuration->Sessions->Block Spiders not set to True? Is there something about the server configuration that has a problem with Force Cookie Use set to False and Block Spiders set to True?

What PHP version is being used?

Do you have a shipping module setup? If so, where in the process to check out process is it set/established? Are the Express Paypal issues being logged when selecting to use paypal directly from the shopping cart page and/or the login screen or further downstream in checkout? If "early on" this would be indicative of a customer not being logged in and perhaps therefore $_SESSION['customer_id'] not being set, although that "possibility" depends a little on the answer to the questions of this paragraph which would then lead to additional code review to see the likelihood of that situation existing.

The remaining log entries appear to relate to the above which appears to be a situation of an individual checking out through PayPal Express without logging in and that session settings bypass some code that probably should be updated to prevent at least the first couple of messages.