It's very convenient if you put the guitar beside the bed so that you can play it at any time. However, if you put the guitar on the bed or next to the pillow, it may affect your sleep. Some guitars look like mirrors because they are waxed. Mirrors usually affect people's sleep.
So you can choose to put the guitar beside the bed so that you can play it at any time. However, if you find that the guitar affects sleep, you may need to adjust the position of the guitar or choose other instruments to practice.