I had a right game with my tomy monitor when we used it first of all. Yes, check the temp isn't too high in bab's room, but also make sure you're getting a good connection, i.e. your parent monitor isn't out of range. Check the band on the side of the monitor is A or B and which ever you choose it matches the baby unit. Then mess about with positioning until you stop getting the bleeping. We live in a long victorian house and i think that may have been a problem; we had to be really picky where we set up the parent unit. It was a pain, to tell the truth!
When we dug out our tomy monitor when second baby was born it beeped continually, I phoned Tomy and discovered something was wrong with the parent unit. They do repairs or you can by replacement units for £15.