site stuck due to low memory and it is also depend space.
the numbers of plugin you are using (if you delete some but they still consuming memory)
try to reduce plugin, and use plugin garbage collection.
it may be due to cache issue, you need to clear cache or try to use any cache plugin that will help you for speed also.
hope it will help you, if your problem not solve leave a message will try to solve.
]]>define( 'WP_MEMORY_LIMIT', '256M' );
If that doesn`t help you might want to get in touch with your hosting company for more details on how to do this.
]]>Best
Fabio
]]>