The source of the problem seems to come from having your Mac in sleep mode while still connected to the display. In light of that, whenever you put your Mac to sleep, disconnect the display from your Mac.
First of all, you should test the cable that connects your display to your Mac and see if that's the problem. If the connection isn't the problem, make sure your display is actually turning on and try unplugging/plugging in your cables. If it still doesn't work, try resetting your SMC How to reset the System Management Controller (SMC) on your Mac and NVRAM/PRAM Reset NVRAM or PRAM on your Mac on your Mac.