In the mongodb.log file can see error when the problem occurs:
2020-03-05T16:00:37.160+0000 I CONTROL [conn11] mongod.exe ...\src\mongo\util\signal_handlers_synchronous.cpp(361) mongo::reportOutOfMemoryErrorAndExit+0x90

This is for MongoDB v3.6.14 but could occur for other versions also

MongoDB is falling over due to "reportOutOfMemoryErrorAndExit" i.e. the root cause is most likely a lack of physical memory for the server
The first thing to check is whether the Windows Server itself is low on available memory, as this error can occur if there is no more memory being made available to Mongo.
Also check the Windows Event logs for the date/time around which the errors have occured and confirm any which seem relevant