Weird Startup

[Wheely]

Within the last week my PC has been starting very strangely and I wondered if anyone here recognised the symptoms.

I turn my PC on as normal using the power switch and the large fan on the top starts spinning, then slows down, then spins again and it keeps doing this. The monitor does not show the PC booting at all.

Then if I hold down the power button to turn it off, when I turn it back on the 2nd time it all kicks in to life and boots properly.

This happens when I try to turn it on either in the morning or when I get home from work, aka after a period of time of not using it.

Any ideas what is going on or what may be about to fail ?

Any help or ideas would be greatly appreciated.

[truenorth]

If you have access to an other power supply of equal or greater value try that.truenorth
P.s. If this procedure is not something your knowledgeable about please say so and we can assist you.

[Geek-9pm]

If it always has been this way, leave it alone. 

[truenorth]

"Within the last week my PC has been starting very strangely ".truenorth

[Geek-9pm]

"Within the last week my PC has been starting very strangely ".truenorth

My bad. 
The power supply is cycling because of an parent overload. This can be neither a failing PSU or almost any component in the system. Even a DVD drive can do that. Or a hard drive. Or a electrolytic on the motherboard.

it should NOT be necessary to use a larger PSU,