can you run a shell command via nohup at later time?
Are you sure you aren't looking for something like at.
You can use the at (man at) command to do this, and then you don't need the nohup.
If you really wanted to, you could:
nohup bash -c 'sleep 5; command' &
But you might be better off running the command in screen and then use sleep before it so you can easily check the output.
You could create another shell script that does the sleep then runs your command.
cat > x.sh sleep 5 yourcommand.sh ^D nohup x.sh &