Grey screen on waking, running OS X 10.10.3 on iMac 21.5 late 2012

Can you tell me please what is happening when this occurs? Is there any way to fix it? The iMac is slow to wake up sometimes, not always, the mouse takes a long time to become active. I usually have my iPhone and iPad plugged in overnight.

Processor 2.7 GHzIntel Core i5

Memory 8GB 1600MHz DDR3

Graphics NVIDIA GeForce GT640M 512 MB

I have looked at the listed apps in the System Prefs > Security and Privacy > Privacy > Accessibility file. None of them are checked.

Here are the Console powerd logs from today.

2015-05-20 10:06:58.000 AM kernel[0]: PM response took 5121 ms (49, powerd)

2015-05-20 11:55:43.000 AM kernel[0]: PM response took 2003 ms (49, powerd)

2015-05-20 1:44:31.000 PM kernel[0]: PM response took 1980 ms (49, powerd)

2015-05-20 2:07:30.000 PM kernel[0]: PM response took 1994 ms (49, powerd)

2015-05-20 10:22:58.000 PM kernel[0]: PM response took 932 ms (49, powerd)

2015-05-20 10:56:22.000 PM kernel[0]: PM response took 5145 ms (49, powerd)

2015-05-21 12:45:07.000 AM kernel[0]: PM response took 1996 ms (49, powerd)

2015-05-21 2:33:56.000 AM kernel[0]: PM response took 1978 ms (49, powerd)

2015-05-21 4:22:44.000 AM kernel[0]: PM response took 1998 ms (49, powerd)

2015-05-21 6:11:32.000 AM kernel[0]: PM response took 1982 ms (49, powerd)

2015-05-21 8:00:20.000 AM kernel[0]: PM response took 2006 ms (49, powerd)

2015-05-21 9:53:45.000 AM kernel[0]: PM response took 5076 ms (49, powerd)

2015-05-21 10:54:36.000 AM kernel[0]: PM response took 4092 ms (49, powerd)

2015-05-21 12:43:22.000 PM kernel[0]: PM response took 1990 ms (49, powerd)

2015-05-21 2:32:11.000 PM kernel[0]: PM response took 3142 ms (49, powerd)

2015-05-21 2:55:09.000 PM kernel[0]: PM response took 1990 ms (49, powerd)

2015-05-21 10:01:18.000 PM kernel[0]: PM response took 8890 ms (49, powerd)

2015-05-21 10:23:04.000 PM kernel[0]: PM response took 5110 ms (49, powerd)

2015-05-22 12:11:49.000 AM kernel[0]: PM response took 2002 ms (49, powerd)

2015-05-22 2:00:38.000 AM kernel[0]: PM response took 2001 ms (49, powerd)

2015-05-22 3:49:26.000 AM kernel[0]: PM response took 1997 ms (49, powerd)

2015-05-22 5:38:14.000 AM kernel[0]: PM response took 1994 ms (49, powerd)

2015-05-22 7:27:02.000 AM kernel[0]: PM response took 1994 ms (49, powerd)

2015-05-22 12:07:57.000 PM kernel[0]: PM response took 5108 ms (49, powerd)

2015-05-22 1:56:41.000 PM kernel[0]: PM response took 1998 ms (49, powerd)

2015-05-22 3:45:29.000 PM kernel[0]: PM response took 1996 ms (49, powerd)

2015-05-22 4:08:29.000 PM kernel[0]: PM response took 2006 ms (49, powerd)

2015-05-23 8:39:01.000 AM kernel[0]: PM response took 27826 ms (49, powerd)

Thank you very much for your help with this.

Best regards!!

Sue