I started to have the same issue in 4.19 a week ago and now it freezes editor/standalone game for several seconds every several seconds. Before last week i never seen this issue but i was told that some of our team members have seen it sometimes rare in 4.18 before.
As i can see i have the same issue as user **** wrote. We have steam and gamesparks integration, and it seems gamesparks causing it, because if i disable gamesparks then the engine stops freezing.
in logs i can only see the next lines and i have added comment how it happens:
[2018.06.05-17.54.33:010][416]UGameSparksModuleLog: Create new connection
**here goes 13 seconds of freeze**
[2018.06.05-17.54.46:143][227]UGameSparksModuleLog: Connection not ready in time, deleting it
[2018.06.05-17.54.46:144][227]UGameSparksModuleLog: WebSocket closed
**here goes 21 seconds of normal engine work**
[2018.06.05-17.55.07:149][228]UGameSparksModuleLog: Create new connection
**here goes 18 seconds of freeze**
[2018.06.05-17.55.25:085][337]UGameSparksModuleLog: Connection not ready in time, deleting it
[2018.06.05-17.55.25:085][337]UGameSparksModuleLog: WebSocket closed
and it repeates infinitely