abnormal logout debugging

I am getting some abnormal behaviour lately from my Ubuntu 14.04.4 LTS Desktop machine. With no apparent reason or failure, all program close and I get logged out. I have also noticed lately a lot of WebGL chrashes in my Chromium and Chrome. I have no idea if is some hardware or software failure, although the fact that is not a full restart, but only a logout makes me think is a software issue.

I was looking at /var/log/syslog and I have this logs since last restart which does not point me to a specific error:

Apr  1 09:49:40 v24 NetworkManager[910]:  error requesting auth for org.freedesktop.NetworkManager.wifi.share.open: (3) GDBus.Error:org.freedesktop.DBus.Error.NameHasNoOwner: GDBus.Error:org.freedesktop.DBus.Error.NameHasNoOwner: Could not get UID of name ':1.439': no such name
Apr  1 09:49:40 v24 colord: device removed: xrandr-Goldstar Company Ltd-E2750-010MAAKDF872
Apr  1 09:49:40 v24 colord: Profile removed: icc-a8ff8ebef3b548f46e2eddd5c6ba1217
Apr  1 09:49:42 v24 dbus[565]: [system] Activating service name='org.freedesktop.systemd1' (using servicehelper)

Apr  1 09:49:42 v24 dbus[565]: [system] Successfully activated service 'org.freedesktop.systemd1'
Apr  1 09:49:42 v24 rtkit-daemon[1419]: Successfully made thread 7851 of process 7851 (n/a) owned by '1000' high priority at nice level -11.
Apr  1 09:49:42 v24 rtkit-daemon[1419]: Supervising 6 threads of 2 processes of 2 users.
Apr  1 09:49:42 v24 pulseaudio[7851]: [pulseaudio] pid.c: Stale PID file, overwriting.
Apr  1 09:49:42 v24 gnome-session[7701]: WARNING: Could not parse desktop file fluxgui.desktop or it references a not found TryExec binary
Apr  1 09:49:42 v24 rtkit-daemon[1419]: Successfully made thread 7865 of process 7851 (n/a) owned by '1000' RT at priority 5.
Apr  1 09:49:42 v24 rtkit-daemon[1419]: Supervising 7 threads of 2 processes of 2 users.
Apr  1 09:49:42 v24 rtkit-daemon[1419]: Successfully made thread 7867 of process 7851 (n/a) owned by '1000' RT at priority 5.
Apr  1 09:49:42 v24 rtkit-daemon[1419]: Supervising 8 threads of 2 processes of 2 users.
Apr  1 09:49:43 v24 rtkit-daemon[1419]: Successfully made thread 7904 of process 7851 (n/a) owned by '1000' RT at priority 5.

Apr  1 09:49:43 v24 rtkit-daemon[1419]: Supervising 9 threads of 2 processes of 2 users.
Apr  1 09:49:43 v24 rtkit-daemon[1419]: Successfully made thread 7908 of process 7851 (n/a) owned by '1000' RT at priority 5.
Apr  1 09:49:43 v24 rtkit-daemon[1419]: Supervising 10 threads of 2 processes of 2 users.
Apr  1 09:49:43 v24 rtkit-daemon[1419]: Successfully made thread 7913 of process 7913 (n/a) owned by '1000' high priority at nice level -11.
Apr  1 09:49:43 v24 rtkit-daemon[1419]: Supervising 11 threads of 3 processes of 2 users.
Apr  1 09:49:43 v24 pulseaudio[7913]: [pulseaudio] pid.c: Daemon already running.
Apr  1 09:49:43 v24 rtkit-daemon[1419]: Successfully made thread 7915 of process 7915 (n/a) owned by '1000' high priority at nice level -11.
Apr  1 09:49:43 v24 rtkit-daemon[1419]: Supervising 12 threads of 4 processes of 2 users.
Apr  1 09:49:43 v24 pulseaudio[7915]: [pulseaudio] pid.c: Daemon already running.
Apr  1 09:49:43 v24 dbus[565]: [system] Activating service name='org.freedesktop.locale1' (using servicehelper)

Apr  1 09:49:43 v24 dbus[565]: [system] Successfully activated service 'org.freedesktop.locale1'
Apr  1 09:49:43 v24 colord: Device added: xrandr-Goldstar Company Ltd-E2750-010MAAKDF872
Apr  1 09:49:43 v24 colord: Automatic metadata add icc-6b6960b48cebea3c9fcce46bc55028fb to xrandr-Goldstar Company Ltd-E2750-010MAAKDF872
Apr  1 09:49:43 v24 colord: Profile added: icc-6b6960b48cebea3c9fcce46bc55028fb

I am looking for suggestions on how to start investigating what is going on.

UPDATE

$ last -f /var/log/wtmp
    valugi   pts/4        :0               Thu Apr  7 15:22   still logged in   
    valugi   pts/1        :0               Thu Apr  7 13:19   still logged in   
    valugi   pts/17       :0               Thu Apr  7 13:03 - 13:04  (00:00)    
    valugi   :0           :0               Thu Apr  7 13:03   still logged in   
    reboot   system boot  3.13.0-85-generi Thu Apr  7 13:03 - 15:24  (02:21)    
    valugi   pts/10       :0               Thu Apr  7 12:47 - 13:01  (00:13)    
    valugi   pts/3        :0               Thu Apr  7 12:45 - 12:52  (00:06)    
    valugi   :0           :0               Thu Apr  7 12:23 - down   (00:37)    
    valugi   pts/11       :0               Thu Apr  7 11:38 - 12:23  (00:44)    

    valugi   pts/3        :0               Tue Apr  5 07:01 - 12:23 (2+05:22)   
    valugi   pts/10       :0               Mon Apr  4 17:21 - 12:23 (2+19:01)   
    valugi   :0           :0               Mon Apr  4 17:21 - 12:23 (2+19:01)   
    valugi   pts/6        :0               Mon Apr  4 10:26 - 17:20  (06:53)    
    valugi   pts/15       :0               Mon Apr  4 00:09 - 17:20  (17:11)    
    valugi   pts/6        :0               Sun Apr  3 22:53 - 23:07  (00:13)    
    valugi   pts/3        :0               Sun Apr  3 22:08 - 17:20  (19:12)    
    valugi   :0           :0               Sun Apr  3 20:35 - 17:20  (20:45)    
    valugi   pts/9        :0               Fri Apr  1 09:49 - 20:35 (2+10:45)   
    valugi   :0           :0               Fri Apr  1 09:49 - 20:35 (2+10:45)