Hi there what kind of tortoise do you have ? my 2 hermans tortoise did the excact same thing untill we got better lighting and heat lamps are you using the correct lighting and heat lamps? if not i would suggest getting some and put the lamp at one end and a bed at the other end that way when they get too hot they can cool down remember when a tortoise is cold it tends to want to sleep and not do anything there body has to be a certain tempature before they can digest food