I recently build my first PC with no problems (good start). I have had it running for about a month and know i have the problem.
I use the moon button on my key board to sleep it but when i wiggle the mouse to wake it up the computer fans start spinning and such and then it just cuts out. It then restarts does the same, turns off again, does that a couple time then eventually turns on.
However when it turns on it is very unresponsive and programs crash easily, so must be reset again.
The easy answer is don't put your computer to sleep With a 350W power supply, you aren't doing your computer a lot of good going into and coming out of sleep. It is more than likely under amping the graphics card which trips the system and reboots. Then it sounds like the RAM isn't stable on restart and take a couple tries for the timings to reconfigure to get a post.
If you really want to able to sleep, I'd go into your power settings (control panel > system and security > power options) and select high performance so it doesn't cut power to your card when you sleep. If that doesn't let you sleep...I just wouldn't sleep.