We have 2 toilets in the house where the bowl water seems to slowly drain out over 10-30 minutes, and then the toilet flushes itself. Any help would be much appreciated !

We have 2 toilets in the house where the bowl water seems to slowly drain out over 10-30 minutes, and then the toilet flushes itself. Any help would be much appreciated !
And this happens to both toilets? Is there any gurgles from any other fixture?

then the toilet flushes itself Are you saying the tank opens up and flushes or that the rest of the water left in the bowl just drains,( does it really
Flush or simply drain away?) down to nothing? More details please. Tom