Erreur : Gateway Timeout The gateway did not receive

Bonjour,

Depuis 5 jours, mon site affiche souvent ce message d'erreur : " Gateway Timeout The gateway did not receive a timely response from the upstream server or application. "

Parfois, ça marche, mais au bout de quelques secondes, ça affiche à nouveau ce message Gateway Timeout. Là, ce soir, impossible de travailler sérieusement sur mon site sans que ce message réapparait souvent.

Y a t il un moyen de savoir qu'est-ce qui cause cela ?

Alors voici ma configuration :
Version PHP globale 7.2, environnement stable
Offre Pro 90plan
site : https://www.herbesdechine.com
environ 50 visiteurs par jour
Woocommerce, site en reconstruction

Pour les logs "out", voici une partie du copiée/collée :

[2018 Mar 17 00:02:52] [340515.289661] TCP:45992 => 213.186.33.2:443
[2018 Mar 17 00:04:40] [340623.398543] TCP:48230 => 213.186.33.2:443
[2018 Mar 17 00:07:05] [340768.192937] TCP:34426 => 192.0.78.25:443
[2018 Mar 17 00:07:44] [340807.259437] TCP:51476 => 213.186.33.2:443
[2018 Mar 17 00:09:50] [340933.145929] TCP:53262 => 213.186.33.2:443
[2018 Mar 17 00:10:17] [340960.418039] TCP:53954 => 213.186.33.2:443
[2018 Mar 17 00:15:09] [341252.300743] TCP:58370 => 213.186.33.2:443
[2018 Mar 17 00:16:44] [341347.099405] TCP:59658 => 213.186.33.2:443
[2018 Mar 17 00:16:55] [341357.894224] TCP:59784 => 213.186.33.2:443
[2018 Mar 17 00:34:45] [628972.705470] TCP:37968 => 213.186.33.2:443
[2018 Mar 17 00:22:03] [341665.719026] TCP:36632 => 213.186.33.2:443
[2018 Mar 17 00:22:09] [341672.231927] TCP:36850 => 213.186.33.2:443
[2018 Mar 17 00:26:47] [341949.721878] TCP:41222 => 213.186.33.2:443
[2018 Mar 17 00:30:33] [342176.539802] TCP:44808 => 213.186.33.2:443
[2018 Mar 17 00:37:46] [342609.163229] TCP:51528 => 213.186.33.2:443
[2018 Mar 17 00:38:40] [342663.020604] TCP:52250 => 213.186.33.2:443
[2018 Mar 17 00:44:37] [343019.779924] TCP:58476 => 213.186.33.2:443
[2018 Mar 17 00:45:39] [343082.311068] TCP:59838 => 213.186.33.2:443
[2018 Mar 17 00:46:32] [343135.467870] TCP:60682 => 213.186.33.2:443
[2018 Mar 17 00:47:03] [343165.940105] TCP:32896 => 213.186.33.2:443

etc... Quelqu'un a une idée ?