Updates for your YouTube app are likely to remedy the problem, especially if it's caused by problems that disrupt the program's usual functioning. Aside from introducing new features, developers update their programs on a regular basis to fix software flaws, such as the one you're now experiencing. With that in mind, check to see whether your YouTube app needs to be updated. To begin, go to the App Store, then scroll down to the bottom right corner of your iPhone screen and hit Updates.