i had this same problem with my motorola i had a while ago.. it wouldnt turn on properly for like 24 hours and went to the motorola logo, then went to a white screen.. so i took the battery out and left it alone for 12 hours.. then put the battery back in and plugged it on for it to charge and turned it on while it was charging and it turned on and worked fine..
i asked my friend and he said that if phones are kept on 24/7 they hit an overheating, exaustion kind of thing and start playing up.. so maybe every now and then, turn it off for 12 hours and let it cool off before using it again...