imac shutting down abnormally and not restarting

My iMac is shutting down abruptly. When I press the power button, no response. After I detach the power chord for a minute and press power button it restarts. But again shuts down abruptly.

Following is reportrt generated by EtreCheck, about which I came to know from apple discussion forum.

EtreCheck version:4.3.1 (4D024)

Report generated:2018-05-24 15:38:38

Download EtreCheck from https://etrecheck.com

Runtime:4:16

Performance:Good

Problem:Computer is restarting

Description:

iMac shutting down randomly and not starting

Major Issues:

Anything that appears on this list needs immediate attention.

No Time Machine backup- Time Machine backup not found.

Minor Issues:

These issues do not need immediate attention but they may indicate future problems.

Apps crashing- There have been numerous app crashes.

Unsigned files- There is unsigned software installed. They appear to be legitimate but should be reviewed.

32-bit Apps- This machine has 32-bits apps that may have problems in the future.

Abnormal shutdown- Your machine shut down abnormally.

Hardware Information:

iMac (27-inch, Late 2013)

iMac Model: iMac14,2

1 3.2 GHz Intel Core i5 (i5-4570) CPU: 4-core

8 GB RAM -Upgradeable

BANK 0/DIMM0 - 4 GB DDR3 1600 ok

BANK 1/DIMM0 - 4 GB DDR3 1600 ok

BANK 0/DIMM1 - Empty

BANK 1/DIMM1 - Empty

Video Information:

NVIDIA GeForce GT 755M - VRAM: 1024 MB

iMac 2560 x 1440

Drives:

disk0 - APPLE HDD ST1000DM003 1.00 TB (Mechanical)

Internal SATA 3 Gigabit Serial ATA

disk0s1 - EFI (MS-DOS FAT32) [EFI] 210 MB

disk0s2 [Core Storage Container] 999.35 GB

disk1 - Macintosh HD (Journaled HFS+) 999.01 GB

disk0s3 - Recovery HD (Journaled HFS+) [Recovery] 650 MB

Mounted Volumes:

disk1 - Macintosh HD 999.01 GB (851.32 GB free)

Journaled HFS+

Mount point: /

Network:

Interface en0: Ethernet

Interface en1: Wi-Fi

802.11 a/b/g/n/ac

One IPv4 address

Interface en5: iPhone

Interface en4: Bluetooth PAN

Interface bridge0: Thunderbolt Bridge

iCloud Quota: 1.99 GB available

System Software:

macOS High Sierra 10.13.4 (17E202)

Time since boot: Less than an hour

System Load: 1.57 (1 min ago) 1.54 (5 min ago) 1.32 (15 min ago)

Security:

System	Status
Gatekeeper	Mac App Store and identified developers
System Integrity Protection	Enabled

Unsigned Files:

Launchd: /Library/LaunchDaemons/com.microsoft.office.licensing.helper.plist

Executable: /Library/PrivilegedHelperTools/com.microsoft.office.licensing.helper

Details: Exact match found in the whitelist - probably OK

32-bit Applications:

24 32-bit apps

System Launch Agents:

[Not Loaded]	9 Apple tasks
[Loaded]	178 Apple tasks
[Running]	105 Apple tasks
[Other]	One Apple task

System Launch Daemons:

[Not Loaded]	36 Apple tasks
[Loaded]	187 Apple tasks
[Running]	112 Apple tasks

Launch Agents:

[Not Loaded]	com.teamviewer.teamviewer_desktop.plist (TeamViewer GmbH - installed 2017-08-24)
[Not Loaded]	com.teamviewer.teamviewer.plist (TeamViewer GmbH - installed 2017-08-24)

Launch Daemons:

[Not Loaded]	com.teamviewer.teamviewer_service.plist (TeamViewer GmbH - installed 2017-08-24)
[Loaded]	com.apple.installer.osmessagetracing.plist (Apple - installed 2018-04-18)
[Loaded]	com.teamviewer.Helper.plist (TeamViewer GmbH - installed 2017-08-24)
[Loaded]	com.adobe.fpsaud.plist (Adobe Systems, Inc. - installed 2018-04-29)
[Loaded]	com.microsoft.office.licensing.helper.plist (? 6d8cb30e - installed 2010-08-25)

User Launch Agents:

[Other]	com.google.keystone.agent.plist (Google, Inc. - installed 2018-02-04)
[Loaded]	com.skype.skype.shareagent.plist (Skype Communications S.a.r.l - installed 2018-02-13)

User Login Items:

iTunesHelper Application (Apple - installed 2018-05-22)

(/Applications/iTunes.app/Contents/MacOS/iTunesHelper.app)

Google Chrome Application (Google, Inc. - installed 2018-05-22)

(/Applications/Google Chrome.app)

Backup and Sync Application (Google, Inc. - installed 2018-04-13)

(/Applications/Backup and Sync.app)

Internet Plug-ins:

FlashPlayer-10.6: 29.0.0.171 (installed 2018-05-23)

QuickTime Plugin: 7.7.3 (installed 2018-03-28)

Flash Player: 29.0.0.171 (installed 2018-05-23)

SharePointBrowserPlugin: 14.0.0 (installed 2010-08-25)

3rd Party Preference Panes:

Flash Player (installed 2018-04-29)

TeXDistPrefPane (installed 2015-09-27)

Time Machine:

Time Machine Not Configured!

Top Processes by CPU:

Process (count)	Source	% of CPU	Location
sandboxd	Apple	9
WindowServer	Apple	6
kernel_task	Apple	3
diagnosticd	Apple	1
Console	Apple	0

Top Processes by Memory:

Process (count)	Source	RAM usage	Location
Google Chrome Helper (11)	Google, Inc.	1.42 GB
kernel_task	Apple	763 MB
mdworker (29)	Apple	753 MB
Google Chrome	Google, Inc.	351 MB
MTLCompilerService (14)	Apple	248 MB

Top Processes by Network Use:

Process	Source	Input	Output	Location
mDNSResponder	Apple	20 MB	275 KB
netbiosd	Apple	1 MB	59 KB
rapportd	Apple	384 B	396 B
SystemUIServer	Apple	0 B	64 B
kernel_task	Apple	0 B	0 B

Top Processes by Energy Use:

Process (count)	Source	Energy (0-100)	Location
WindowServer	Apple	2
Console	Apple	0
Google Chrome	Google, Inc.	0
diagnosticd	Apple	0
mDNSResponder	Apple	0

Virtual Memory Information:

Available RAM	2.39 GB
Free RAM	20 MB
Used RAM	5.61 GB
Cached files	2.37 GB
Swap Used	0 B

Software Installs (past 30 days):

Name	Version	Install Date
iTunes	12.7.4	2018-05-22
Security Update 2018-001	2018-05-22
MRTConfigData	1.32	2018-05-22
Gatekeeper Configuration Data	138	2018-05-22
Numbers	5.0	2018-05-22
Pages	7.0	2018-05-22
Keynote	8.0	2018-05-22
Adobe Flash Player	29.0.0.171	2018-05-23

Diagnostics Information (past 7 days):

2018-05-24 15:11:07 Last Shutdown Cause: 0 - Power loss

2018-05-22 15:59:34 imagent.app Crash

/System/Library/PrivateFrameworks/IMCore.framework/imagent.app

objc[426]: NSError object 0x7fdae6618510 overreleased while already deallocating; break on objc_overrelease_during_dealloc_error to debug

2018-05-22 13:15:41 IMRemoteURLConnectionAgent Crash (18 times)

/System/Library/PrivateFrameworks/IMFoundation.framework/XPCServices/IMRemoteURL ConnectionAgent.xpc/Contents/MacOS/IMRemoteURLConnectionAgent

*** CFEqual() called with NULL first argument ***

End of report