Hi,
I thought long about adding something to this post, but then decided against it, because my problem is different from: How to delay Hass startup?
I need a delay during the startup phase of HA. I have a device that is called five times during startup (for 5 different switches / sensors). The REST interface of that device is quite slow, so different calls from HA are not finished yet while the next is already issued. At least 1, often 2 switches / sensors are always left out. Only after 5 to 10 restarts I can get it to find all 5 … by chance 
Therefore, I’d rather slow down HA’s startup with 20 second pauses (call 1, pause 20 secs, call 2, pause 20 secs etc.) instead of hoping for the best.
Any ideas?