I had these same error message but not that often when I execute docker ps:
Cannot connect to the Docker daemon at tcp://localhost:2375. Is the docker daemon running?
Sys info: Running Windows 10 Enterprise Vers 1803 OS Build 17134.1069 and docker ver Docker version 18.09.7, build 2d0083d.
I had tried:
-"/localhost:2375 without TLS" verified it was checked
-Reset permissions to local hard drives
-Restarted docker itself few times
Currently running docker via WSL. Everything works fine but every blue moon I get this error. No matter what I do, it will not go away. My current solution is to do a hard cold restart and everything works as before. I have a theory and it is that docker (or docker-machine and underlined layer) builds up some memory over time until it reaches at limit and the connection cannot be made. Maybe the port is not release properly? It takes on average 10 to 15 days to reach this error and for me, restarting the system solved the problem every time. This has been my experience in the last three months so this behavior of locking up is consistent. I would like to note that after I restart the machine, Docker works without any problems.
Cheers!