The apache2 instance did not start within 20 seconds

i got this error tonight, literally only this:

 * Restarting web server apache2                                                                              [fail] 
 * The apache2 instance did not start within 20 seconds. Please read the log files to discover problems

and this is the error.log

[Wed Jun 08 21:26:12.702116 2016] [ssl:warn] [pid 3006] AH02292: Init: Name-based SSL virtual hosts only work for clients with TLS server name indication support (RFC 4366)
    [Wed Jun 08 21:26:13.000381 2016] [:notice] [pid 3006] ModSecurity for Apache/2.7.7 (http://www.modsecurity.org/) configured.
    [Wed Jun 08 21:26:13.000435 2016] [:notice] [pid 3006] ModSecurity: APR compiled version="1.5.1-dev"; loaded version="1.5.1-dev"
    [Wed Jun 08 21:26:13.000443 2016] [:notice] [pid 3006] ModSecurity: PCRE compiled version="8.31 "; loaded version="8.38 2015-11-23"
    [Wed Jun 08 21:26:13.000458 2016] [:warn] [pid 3006] ModSecurity: Loaded PCRE do not match with compiled!
    [Wed Jun 08 21:26:13.000461 2016] [:notice] [pid 3006] ModSecurity: LUA compiled version="Lua 5.1"
    [Wed Jun 08 21:26:13.000464 2016] [:notice] [pid 3006] ModSecurity: LIBXML compiled version="2.9.1"

how can i trouble shoot this??