Q: blink red light but starts back up-how to fix?

mac pro 4,1 xeon quad core 2.6ghz. 8gig ram el capitan.. ati radeon hd 5770 1024 mb.

     This has been a nagging problem for a long time now on and off- When I set my computer to never sleep in prefs., there are no problems- it just stays on almost always without shutting down. But,when I set computer to sleep,it shuts off at the sleep moment and red light blinks after that. But then,I can start it right back up again. I just cannot shut to down with out the red blinking light which is accompanied by a click sound. Somehow,I don't think this should be happening. I have read many responses to others with similar problems but this problem seems unique. I did do the pram reset- n nothing changed. I did reseat the ram. My question is then,could it be the third party graphics card? I also an poem sad 240 drive. but when i switched back to the original hd it didn't make a difference with the blinking..

Does the blinking use extra power I wonder? I might just pick up another used similar mac pro and swap in my own drive if I cannot fix this problem..

thanks for your help. I hope that I was able to give proper info.