Macbook Pro 2011 freezes randomly

Hi there, so my problem is that my Macbook Pro early 2011 (8,2) will sometimes randomly freeze (can't move cursor or anything) for a few seconds, shuts down, then I have to restart it. No spinning wheel or anything pops up, and it just reboots normally and everything works fine until it freezes again. I was using Safari when it happened today and yesterday on YouTube. My Processor is 2 GHz Intel Core i7 and memory is 16 GB 1333 MHz DDR3l, Graphics is Intel HD Graphics 3000 512 MB running OS X Yosemite Version 10.10.3

I should also mention that after it froze yesterday, it shut down and I restarted it, and there would be the startup sound but no display screen (it made the sound but the screen remained off and black). This happened several times at startup. I then did a PRAM reset which didn't work, and then an SMC reset which did the trick and started up normally. This is the only time that happened.

The freezes happen only once a day to several times a day, or go a day working fine. I have just recently (about a week) installed a Samsung 850 EVO SSD 500gb and Crucial RAM 16gb, and I'm enjoying the upgrade except for when it randomly freezes. I've searched everywhere and can't find the right solution.. Could it be a logic board problem? Should I take it in for service? I've had to do a logic board and HDD replacement over the years, and I'm getting worried I might have to pay more again.

It happened around 3:59 pm today and I went to Console and got these messages around the time when it happened - maybe they can help, although I have no idea what they mean:

6/29/15 3:58:19.699 PM com.apple.xpc.launchd[1]: (com.apple.imfoundation.IMRemoteURLConnectionAgent) The _DirtyJetsamMemoryLimit key is not available on this platform.

6/29/15 3:58:20.151 PM sandboxd[273]: ([422]) com.apple.WebKit(422) deny file-read-data /Applications/32 Lives.app/Contents/Resources/TTLWrapperPlugin.dylib

6/29/15 3:58:21.679 PM com.apple.xpc.launchd[1]: (com.apple.imfoundation.IMRemoteURLConnectionAgent) The _DirtyJetsamMemoryLimit key is not available on this platform.

6/29/15 3:58:21.950 PM com.apple.xpc.launchd[1]: (com.apple.imfoundation.IMRemoteURLConnectionAgent) The _DirtyJetsamMemoryLimit key is not available on this platform.

6/29/15 3:58:24.388 PM com.apple.xpc.launchd[1]: (com.apple.WebKit.Networking.B397B573-8910-4736-96C1-74DFE7E8C510[416]) Service exited with abnormal code: 1

6/29/15 4:03:43.353 PM com.apple.xpc.launchd[1]: (com.apple.imfoundation.IMRemoteURLConnectionAgent) The _DirtyJetsamMemoryLimit key is not available on this platform.

6/29/15 4:04:14.665 PM com.apple.xpc.launchd[1]: (com.apple.imfoundation.IMRemoteURLConnectionAgent) The _DirtyJetsamMemoryLimit key is not available on this platform.

6/29/15 4:04:15.335 PM com.apple.xpc.launchd[1]: (com.apple.quicklook[434]) Endpoint has been activated through legacy launch(3) APIs. Please switch to XPC or bootstrap_check_in(): com.apple.quicklook

6/29/15 4:04:28.911 PM CoreServicesUIAgent[232]: Error -60005 creating authorization

6/29/15 4:04:36.277 PM loginwindow[90]: ERROR | -[PersistentAppsSupport saveLogoutPersistentState:finalSnapshot:] | Attempt to insert app with NULL bundle ID

Any help would really really be appreciated!