Lately my Toto toilet is running then stopping even though no one is using it. Sounds like water is going into the tank at odd times. I do notice a small stream at the back of the bowl right after flushing. Can anyone advise where the problem could be. I am an absolute novice at this but would like to diy it if at all possible. Thanks for any help you can give.

the flapper is leaking by.
if you call toto they should send you a new part at no cost.
you will need to give them a model of the toilet.
looks like this..

caution... must be the exact replacement or it won't work right...

If the flapper is not the problem you may just have the fill valves flexible fill TUBE inserted too far down within the overflow tube. This will cause water to siphon from the tank down into the overflow tube. When the tank water level drops enough, the fill valve will then activate to raise the level within the tank back up to the proper full level -- over and over.

Cause
Incorrect fill tube installation when replacing the actual fill valve or other repairs.
Fill tube accidentally pushed too far down within the overflow tube during tank cleaning.

Solution
Simply raise the end of the fill tube above the tanks "full" level and secure it with a stainless steel or plastic clip.

See youtube " Water running from the toilet? Might be the refill tube "

Thanks. I did a leak test(recommended by Toto)and it was, as you wrote, the flapper. We replaced it and it seems to be working fine now. Thanks, again, for the quick help.