Short answer
Yes. You can do dhikr, make dua and send salawat without wudu, lying down, walking or driving, at any time of day. Even in janabah or during a period, dhikr and dua are allowed; only reciting the Quran as Quran is not. The one exception is the toilet, where spoken dhikr is disliked.
Dhikr, tasbih, dua and salawat are permissible without wudu and in any posture, and wudu for them is mustahabb only. A person in janabah, hayd or nifas may do dhikr and dua, including Quranic duas said with the intention of dua. Saying dhikr aloud in the toilet is makruh.
The four schools agree on this.
Explanation
Allah praises those "who remember Allah while standing or sitting or lying on their sides" (3:191). Aisha said the Prophet ﷺ used to remember Allah at all times. The four schools agree that dhikr has no condition of wudu or posture.
- Without wudu: allowed. Wudu is better and adds to the reward, but is not needed.
- Lying down, in bed: allowed. The bedtime adhkar are said lying down: see duas before sleeping.
- While driving, walking or working: allowed, and a good way to fill time.
- Any time of day: there is no forbidden time for dhikr, even the times when salah is not allowed.
- In janabah or on your period: dhikr, dua, salawat and istighfar are allowed. Ayat of the Quran said as dua, such as Rabbana atina, are allowed with the intention of dua. Reciting the Quran as recitation is not: see reading the Quran on your period.
- In the toilet: do not say dhikr aloud; remember Allah in your heart. See reciting in the bathroom.
This ease is what makes dhikr the simplest act of worship to keep up through the day. Counting on your fingers or a tasbih counter works anywhere.
The evidence
Quran, Surah Aal-i-Imraan 3:191
ٱلَّذِينَ يَذْكُرُونَ ٱللَّهَ قِيَٰمًۭا وَقُعُودًۭا وَعَلَىٰ جُنُوبِهِمْ وَيَتَفَكَّرُونَ فِى خَلْقِ ٱلسَّمَٰوَٰتِ وَٱلْأَرْضِ رَبَّنَا مَا خَلَقْتَ هَٰذَا بَٰطِلًۭا سُبْحَٰنَكَ فَقِنَا عَذَابَ ٱلنَّارِ ﴿١٩١﴾
Who remember Allah while standing or sitting or [lying] on their sides and give thought to the creation of the heavens and the earth, [saying], "Our Lord, You did not create this aimlessly; exalted are You [above such a thing]; then protect us from the punishment of the Fire.
Dhikr is praised in every posture.
Sahih Muslim 373
Sahih... كان النبي صلى الله عليه وسلم يذكر الله على كل أحيانه ...
"The Prophet used to remember Allah in all of his states."
Dhikr was not limited to times of wudu.
Where the ruling is recorded
- Nur al-Idah with Maraqi al-Falah, Chapter on menstruation, postnatal bleeding and istihadah. What is forbidden to the junub and the menstruating woman, and that dhikr and dua remain allowed.
- al-Durr al-Mukhtar, Kitab al-Taharah, manners of relieving oneself. Dhikr with the tongue in the toilet is disliked.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.