Cant't connect to admin panel

[bulanel]

Hello,

I have a magento 1.9 that I customized on my localhost.

After I moved it to a new live server I can't log in into the admin panel. It just reloads the key in the URL.

ex of url after hitting log in button:

mydomain/index.php/shopadmin/index/index/key/ef1726ab5d69a037292635e61843befe/?q=%2Findex.php%2Fshopadmin

I check the sessions and the cache.

I kinda try everything that was online regarding this topic and noting worked. 

Any help would be appreciated.

Thank you,

[marcoseduardo]

Sometimes I have the same issue.
I notice that always happens when I try to buy something. After login with some test customer (AND logout) I can not login to the panel again for a long time.