Hello. I Am A 31 Year Old Male And Am

Hello. I am a 31 year old male and am having a pulsating sensation in my anus. I was out taking the yard and sat down and thought my phone was vibrating. Since then (about 2 hours ago) I have had the sensation come about every 5 seconds for 1-2 seconds long. Doesn't hurt just more annoying then anything. Is this normal? What could cause this to happen? Thank you for your help!