Have to keep turning power supply on and off until PC starts

Hello there, recently I've been having a few problems with my PC. When I try to turn it on, the lights will start up, as will the fans, but nothing appears on my screen, my monitor showing a "no signal" message. However, if I keep turning the switch on and off at the back by my power supply, and pressing the power button it will -eventually- turn on.

When it's on it seems to be slower than how it was before I encountered this problem, about a few weeks ago, sometimes programs would randomly stop responding for example.

Is there any simple troubleshooting I can do, to find the issue?

Sorry if this is in the wrong area by the way, mods.

stop turning it off and on< get out the door< do not stop<buy a power supply< go home<replace power supply

LavaKing, you are correct, we jumped like frogs. In the same sense the PSU is easier, like you say, but probably a tad less expensive as well. Much less chance of killing a CPU, RAM or breaking something. I must be lucky, in all of the PC's I've built, last week was the first time I have had a component fail and it was the PSU. It was kind of easy to figure why the box would shut off an hour after running and restart with one button press and die again later. I had added 2 HDD's and was pushing the tolerances of the PSU.
Anyway, we all appreciate other members knowledge and experience.
Thank you

I have been battling this same issue for some time. Dell monitors would not come out of power save on start up. Disconnected USB hubs on screens and things were OK for a while. Plugged in other USB devices to computer and screens would go into power save. Plugged in one too many and computer screamed at me. Ordered a new, bigger PSU (750W) for overnight delivery. Did a back up onto external HDD and on shutdown got a BSOD "Power State Failure". Replaced PSU and with all three screen USB hubs, ext HDD, licence dongles, webcam, bar fridge etc in all USB ports it is running sweet!