Run container at system startup

I thought that --restart always does that as well but on my linux box (used as docker host) it does not work as expected

$ docker ps -a

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
96b7f8fe1e31 jlesage/jdownloader-2 “/init” 21 hours ago Up Less than a second 3129/tcp, 5900/tcp, 0.0.0.0:5800->5800/tcp jdownloader-2

$ uptime
15:30:08 up 22 min, 1 user, load average: 0.40, 0.38, 0.30

So, as you can see the system is up for 22min already but the container just starts in case I hit the command “docker ps -a” ???

This looks very curious to me and I face this behavior on another ubuntu based linux as well.
This does not make sense to me. Is there something I missed apart from a default docker setup? Does it need further tuning to work as expected?

Any help kindly appreciated!