Firefox will often close in the middle of use with no error msg. How do I fix this?

I currently use an aspen a701 tablet. When I first open firefox it takes over a minute to load the first website or two then works fine. After a few minutes of surfing firefox will just close with no warning or error msg and when I reopen it, it opens to the home page and not my previously viewed page before it closed. Can you fix the loading speed and sudden closing? thank you for your time and help