How to pronounce when there are many three-tone Chinese words lined up?

For more than 2 characters of the 3rd tone in a row, it depends on the speaker's habit.
Most of the time, they will split them in groups of two and apply the same rule, for example: 我想买wǒxiángmǎi, 我只买两个wózhǐmáiliǎnggè, 我只有五本书wǒzhíyǒuwúběnshū... I consider this is the most natural way.
But, many people like to use 2nd tone for 3 characters phrases such as: 我想买wóxiángmǎi, 老李想买酒láolǐxiángmáijiǔ,...
Sometimes, the pronunciation also depends on the context of the whole sentence. In a long sentences, it depends on how you pause or when you want to emphasize a word. For example, 我想我应该wóxiǎng / wǒyīnggāi···
In conclusion, there's no specific rules for this. Even my chinese friends sometimes struggling with them.

You need to pay attention to the tone sandhi rules, which are the rules that govern how the tones of adjacent words in a sentence can change and affect each other. For example, if a third-tone syllable is followed by another third-tone syllable, the first syllable will often change to a second tone.
When three consecutive third-tone characters appear together in a sentence, the second syllable should change to a second tone (a rising tone), while the first and third syllables are pronounced as the regular third tone.

When there are two characters together with the third tone the first character becomes the second tone but it is still written with the third tone. Example: nǐ hǎo becomes ní hǎo，老鼠lǎo shǔ becomes láo shǔ，老虎lǎo hǔ becomes láo hǔ

hope this helps, sorry if I have some grammar mistakes I'm learning English and Chinese.

https://youtu.be/Kp3TRGsnRlk
hope this helps