how to stop nginx 302 error

I have a site with Ubuntu 20.04, php 8.1, and nginx 1.23.1. If I restart nginx and php-fpm I can login, browse the site, and everything works. If I wait a certain amount of time with no activity on the site (10-15 minutes?), I start getting 302 Found errors no matter what page I try to go to. If I restart nginx and php-fpm again, everything starts working again. I can't figure out what's causing this. Here is the nginx config file for the site:

server {
        listen 1443 ssl;
        add_header Strict-Transport-Security "max-age=31536000; includeSubdomains" ;
        server_name my_site;
        root /var/www/my_site/htdocs;
        index index.php index.html;

        access_log  /var/log/nginx/my_site.access.log;
        error_log   /var/log/nginx/my_site.error.log;

        ssl_certificate /etc/nginx/ssl/all.my_site.com.crt;

        ssl_certificate_key /etc/nginx/ssl/all.my_site.com.key;

   
        ssl_session_timeout 5m;
        ssl_session_cache shared:SSL:50m;
        ssl_dhparam /etc/ssl/certs/dhparam.pem;
        ssl_protocols TLSv1.1 TLSv1.2;
        ssl_ciphers 'ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-DSS-AES128-GCM-SHA256:kEDH+AESGCM:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA:ECDHE-ECDSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-DSS-AES128-SHA256:DHE-RSA-AES256-SHA256:DHE-DSS-AES256-SHA:DHE-RSA-AES256-SHA:!aNULL:!eNULL:!EXPORT:!DES:!RC4:!3DES:!MD5:!PSK';
        ssl_prefer_server_ciphers on;

        proxy_buffer_size   128k;
        proxy_buffers   4 256k;
        proxy_busy_buffers_size   256k;

        
        fastcgi_buffers 16 16k;
        fastcgi_buffer_size 32k;

        location / {

                try_files $uri =404;

                # pass PHP scripts to FastCGI server
                
                location ~ \.php$ {
                        include snippets/fastcgi-php.conf;

                        fastcgi_pass unix:/run/php/php8.1-fpm.sock;

                        fastcgi_split_path_info ^(.+\.php)(/.+)$;
            
                        fastcgi_param ALL_FILES_PATH /var/www/my_site;
                        fastcgi_param LOCAL_FILES_PATH /var/www/my_site;
                        fastcgi_param SHARED_FILES_PATH /var/www/my_site-web-8.1;

                        fastcgi_read_timeout 604800;
                        include /etc/nginx/fastcgi_params;
                        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;

                }

        }

}

EDIT: It appears that this 302 error is only happening with PHP files. I put a basic html file in and it loads with a 200 response code.