So much lag!

I've been trying to play minecraft all day on the Java Edition on my Laptop and everytime i try to move my character around it lags sooo bad that i can barely move my character. Its like it's stuck! i've already tried to look up my problem to see if I can fix it myself but nothing is working! i mean sometimes it will fix itself and will work fine but then minuets later it will freeze and then start to lag very bad again.