Sorry, I can’t answer the question about using systemd for auto restarting OH. IMHO this is not something that should be done if you have frequent errors.
Have you stopped the Amazon Control Binding and still getting web socket errors?
You can install the OH in the Alexa app and still control most of your devices as the issue is only with the control binding.
EDIT: See this post for a possible solution Web Socket Error on AmazonEchoControl binding every 65 seconds - #56 by J-N-K
You will need to download the jar file and place it in /usr/share/openhab2/addons then restart OH. Or you can use the console as described in the post.